Neuropsychologia

Clinical research has documented a heterogeneous effect of neurodegenerative disorders on creativity. Some disorders are associated with impaired creative performance, while others may preserve, or even enhance, it. However, the underlying cognitive mechanisms that give rise to the heterogeneous behavioural manifestations remain poorly understood. From a theory-driven approach, we conducted a neuropsychological investigation to examine how frontotemporal lobar degeneration (FTLD), and Alzheimer's Disease (AD) differentially affected the cognitive mechanisms underlying creative thought (semantic cognition, episodic memory, executive control functions). In parallel, we assessed participants' verbal creative idea generation performance using the ideational fluency task (also known as the Alternate Uses Task). We analysed data from 24 individuals with FTLD [clinical consensus diagnosis corticobasal syndrome (CBS: n=20) or progressive supranuclear palsy (PSP: n=4)], 24 individuals with clinical consensus diagnosis AD, and 24 healthy individuals. We reached four major conclusions. First, while both disease groups exhibited deficits in controlled semantic retrieval and executive control functions, only participants with AD exhibited degradation in semantic representations and episodic memory. Second, both disease groups generated fewer responses in both typical and creative conditions across objects that were context-free - i.e., associated with multiple contexts (e.g., brick) and context-bound -i.e., associated with a dominant context (e.g., table knife). Third, when given a context-free object prompt, the ability to generate novel responses appeared to be preserved in participants with FTLD, which contrasted with an impaired ability when prompted to give creative uses for the context-bound object. Fourth, participants with AD produced similar levels of response novelty for both context-free and context-bound objects. From a clinical-cognitive neuroscience perspective, this study demonstrates that distinct cognitive profiles resulting from different neurodegenerative conditions yield differential effects on creative thought. As the first study to show that the contextual information of semantic stimuli can mediate the novelty of verbal responses, we suggest that future research should carefully examine how this factor influences creative task performance.

The ability to generate novel creative ideas (divergent thinking) is closely linked with our ability to imagine novel future events (episodic simulation). Here, we employed an individual differences approach to examine whether divergent thinking and episodic simulation are differentially associated with episodic and semantic retrieval ability. In response to object word cues, participants generated meanings and definitions (semantic memory), remembered a past event (episodic memory), imagined a novel future event (episodic simulation), or generated novel uses (divergent thinking). Replicating previous findings, divergent thinking ability was predicted by the number of episodic details generated during episodic simulation. When directly comparing episodic and semantic memory, the strongest predictor of divergent thinking was semantic memory. In contrast, episodic simulation ability was predicted by both episodic and semantic memory. We interpret these findings as support for the semantic scaffold hypothesis of imagination, according to which semantic memory provides the necessary scaffold or framework for flexible expressions of cognition such as divergent thinking and episodic simulation. As episodic simulation, relative to divergent thinking, was associated with both episodic and semantic retrieval, these findings are taken to reflect common reliance on event construction processes recruited during both episodic remembering and imagining.

A long-standing debate surrounding the neural bases of social concepts concerns the role of anterior temporal lobe (ATL). One perspective suggests ATL subregions are dedicated specifically to social knowledge; another suggests the ATLs constitute a domain-general hub for conceptual knowledge, but with graded functional specialisation depending on connectivity to modality specific spokes. The positions have been difficult to adjudicate due to many confounding factors in tests of social and non-social knowledge. We address these challenges via three innovations in assessment of knowledge in frontotemporal dementia (FTD). First, we introduce a new task that controls for several potential confounds. Second, we apply mixed linear models to behavioural data analysis, allowing further control over confounding factors. Third, we extend the mixed-model approach to lesion-symptom mapping, identifying cortical regions where structural pathology yields a disproportionate impairment on social versus non-social knowledge when other factors are controlled. We used these techniques to probe social and non-social knowledge in FTD subtypes: semantic dementia (SD), associated with asymmetric-bilateral ATL atrophy (n=21), and behavioural-variant (bvFTD), characterised by frontoinsular atrophy (n=24). When confounding factors were controlled, people with SD showed an equal impairment for social and non-social concepts, whereas those with bvFTD were disproportionately impaired on social concepts. The differential impairment of social concepts was associated with atrophy in the insula, orbitofrontal and ventromedial prefrontal cortex and other regions implicated in social knowledge generally. The results suggest that the bilateral ATLs constitute a domain-general semantic hub, whereas ventral prefrontal and insula cortex contribute preferentially to knowledge about people.

Taking anothers perspective is a high-level mental skill underlying many aspects of social cognition. Perspective-taking is usually an embodied egocentric process whereby people mentally rotate themselves away from their physical location into the others orientation. This is accompanied by increased theta-band (3-7 Hz) brain oscillations within a widespread fronto-parietal cortical network including the temporoparietal junction. Individuals with autism spectrum disorder (ASD) have been reported to experience challenges with high-level perspective-taking, particularly when adopting embodied strategies. To investigate the potential neurophysiological basis of these autism-related individual differences, we used magnetoencephalography in combination with a well-replicated perspective-taking paradigm in a group of 18 autistic and 17 age-matched non-autistic adolescents. Findings revealed that increasing the angle between self and other perspective resulted in prolonged reaction times for the autistic group during perspective-taking. This was accompanied by reduced theta power across a wide network of regions typically active during social cognitive tasks. On the other hand, the autistic group showed greater alpha power decreases in visual cortex compared with the non-autistic group across all perspective-taking conditions. These divergent theta and alpha power effects, coupled with steeper response time slopes, suggest that autistic individuals may rely more on alternative cognitive strategies, such as mental object rotation, rather than an egocentric embodied approach. Finally, no group differences were found when participants were asked to track, rather than take, anothers viewpoint, suggesting that autism-related individual differences are specific to high-level perspective-taking.

Many forms of memory are thought to rely on visual imagery, but individuals who report lacking visual imagery (aphantasia) can still perform various memory tasks. There is, however, evidence that aphantasia may lead to less detailed autobiographical memories, suggesting there may be deficits in the underlying cognitive processes that support personal memories. One such process is associative memory, which requires binding of different types of information. Here, we tested whether associative visual memory is intact in aphantasia. We assessed 72 self-identified individuals with aphantasia and 77 controls who reported having visual imagery. Participants completed an associative memory task which involved memorising displays where a unique object in a specific location was associated with a particular colour fixation point. Individuals with aphantasia performed equivalently to controls for object locations and outperformed controls on the associated object-identity. In addition, whereas controls were significantly worse at remembering associated object-identity than object-location, individuals with aphantasia showed no such difference. Both groups showed good metacognitive performance evidenced by a positive correlation between confidence and accuracy; there were no significant differences in confidence between the groups. Reported strategies varied between groups: a large proportion of control participants reported using visual imagery and self-reported use of imagery positively correlated with performance. Conversely, individuals with aphantasia mostly reported using nonvisual strategies to remember the associations. Overall, the findings suggest that individuals with aphantasia can form associative memories using nonvisual strategies. Thus, difficulties with autobiographical memory in aphantasia seem unlikely to be due to fundamental issues with associative memory.

Naming pictures from the same semantic category can interfere with subsequent word retrieval. Although the left inferior frontal gyrus (LIFG) has been implicated in resolving this semantic interference, its causal role in this process remains unclear. Across three experiments, we investigated the contribution of the LIFG to interference resolution during blocked-cyclic naming. Experiment 1 tested whether continuous theta-burst stimulation over the LIFG increased semantic interference relative to vertex stimulation. Although the overall interference effect did not differ significantly between stimulation sites, exploratory analyses revealed an unexpected pattern based on the initial context (related vs. unrelated) with which items were named, suggesting that LIFG disruption affected retrieval of previously related items even when they were subsequently named in unrelated contexts. This observation motivated two further experiments examining the consequences of prior naming context more directly. Experiment 2 established that, without stimulation, interference observed in related blocks was no longer evident after the items were redistributed into unrelated blocks. Experiment 3 combined this design with cathodal or sham transcranial direct current stimulation (tDCS) over the LIFG. Planned comparisons showed that cathodal stimulation slowed naming of initially related items both within related blocks and after redistribution into unrelated blocks; corresponding comparisons for items named consistently in unrelated blocks were not significant. The similar patterns across two stimulation methods suggest that LIFG-mediated control may influence both selection under current competition and subsequent retrieval of previously competing words. These findings could be accommodated within a hybrid account in which working memory supports context-guided selection and selection-related control helps recalibrate lexical accessibility, limiting the carryover of interference into subsequent naming.

Empirical evidence from traditional inhibitory control tasks regarding inhibitory deficits in high autistic traits has been mixed, indicating that this issue remains controversial. Although sex differences are widely documented in autistic cognitive profiles, their role in inhibitory gating mechanisms remains underexplored. Given that the expression of inhibitory gating deficits may be modulated by the social versus non-social nature of stimuli, and no prior study has investigated this topic by integrating both sex differences and stimulus domain, we addressed these two questions with the attribute amnesia paradigm. We manipulated stimulus type (non-social vs. social). In Experiment 1, participants performed a location task with animal drawings as targets and were unexpectedly asked to report animal identity on a surprise trial. High autistic trait females showed significantly higher accuracy on the surprise trial than all other groups, reflecting a failure to actively filter out task-irrelevant non-social information, that is, a reduced inhibitory gating efficiency. In Experiment 2, using face stimuli and a self-vs. other-face design, this gating deficit was no longer expressed: all groups performed at chance levels on the identity judgment, regardless of autistic trait level, sex, or face type. This dissociation aligns with a dual-mechanism framework: the inhibitory gating deficit in high autistic trait females is specific to non-social stimuli and masked by camouflaging for social ones. This study demonstrates that the inhibitory gating deficit in high autistic trait females is not a global impairment but rather a stimulus-dependent one, highlighting the need to consider sex and stimulus type.

Visual imagery refers to the mental generation of visual representations of stimuli, while visual working memory involves retaining visual information for a short period without external input. Due to the conceptual overlap between these two constructs, successful performance on visual working memory tasks may rely on the use of visual imagery to rehearse items during the retention interval. Consequently, individuals with aphantasia, who lack voluntary visual imagery, may experience difficulties with such tasks. However, prior research has suggested that some individuals with aphantasia might employ non-visual strategies to compensate for this deficit. In two experiments, we examined visual working memory performance in aphantasic and control participants across a range of stimulus types. In Experiment 1, participants completed a change localization task using color squares and complex fractals; in Experiment 2, stimuli included real words, phonologically valid pseudowords, and phonologically invalid pseudowords. Across both experiments, aphantasic participants demonstrated significantly impaired visual working memory compared to controls. Notably, their performance was equally impaired for stimuli that were easily verbalizable (i.e., colors and words) and those that were not (i.e., fractals and pseudowords). Furthermore, individual differences in visual imagery ability, as measured by the Vividness of Visual Imagery Questionnaire (VVIQ), significantly predicted working memory performance across all stimulus types. These findings provide direct evidence for the critical role of visual imagery in supporting visual working memory.

Can grammatical gender in a bilingual's first language shape gender-stereotype processing in a second language? Spanish (L1)-English (L2) bilinguals (n = 28) and English monolinguals (n = 28) completed an event-related potential (ERP) priming task in which English pronouns (SHE/HE) followed gender-stereotyped English nouns, half of which had gender-marked Spanish translation equivalents (e.g., NURSE 'enfermera/o', SURGEON 'cirujana/o'), and half unmarked translation equivalents (e.g., SINGER 'cantante', JANITOR 'conserje'). Both groups showed asymmetric stereotype priming: male pronouns elicited a larger N400 for incongruent than congruent primes, whereas female pronouns elicited a larger P300 for incongruent than congruent primes. Crucially, only bilinguals showed modulation by Spanish grammatical gender marking: the N400 effect for male pronouns was larger for primes with gender-marked than unmarked Spanish translations. These findings provide neural evidence that grammatical gender in a bilingual's first language can influence gender-stereotype processing in a second language, linking cross-linguistic activation to social cognition.

Humans can create impressive art, make major scientific breakthroughs, and generate creative solutions that solve everyday life problems. But how are these creative activities supported by the brain? This question is of great scientific interest but remains unanswered. New hypotheses, grounded in converging evidence from cognitive neuroscience, are needed to guide breakthroughs in understanding the neural basis of creative thought. It has long been suggested that creativity is a distinct mental function. However, converging clinical-cognitive neuroscience evidence is starting to suggest that creative thought is not functionally distinct but, instead, might arise from general purpose cognitive mechanisms supporting semantic cognition, controlled episodic memory retrieval, and executive mechanisms (i.e., Cognitive Cornerstones Hypothesis; Chan et al., 2023). Results from this large-scale activation likelihood estimation (ALE) meta-analysis, based on 787 experiments with 10,357 foci from 17,228 healthy adult participants, showed that the brain regions implicated in creativity tasks heavily overlap with the brain regions implicated in the cognitive cornerstones of creative thought (i.e., pre-existing knowledge and executive mechanisms). These striking results suggest that innovative insights will arise from considering the roles of these fundamental cognitive functions and their interactions in supporting creative thought.

The goal of this study was to investigate a relatively unstudied memory condition for paradoxical combinations of item + source memory confidence responses, which challenged the conventional views of the memory processes supporting item and source memory judgments. We studied instances in which people provided accurate source memory judgments (conventionally ascribed as representing recollection) after having first produced low- confidence item recognition hits for the same items (conventionally thought to reflect familiarity-based processing). This paradoxical combination does not fit traditional accounts of being recollection (because it had low-confidence recognition) nor accounts of familiarity (since it had accurate source memory), and event-related potentials (ERPs) were used to adjudicate which processes support these kinds of memories. ERP results were unlike the conventional ERP effects of memory, lacking both an FN400 and the parietal old-new effect (LPC), and instead exhibited a significant negative-going ERP effect occurring later in time (800-1200ms) in central-parietal sites. Behavioral measures of response times revealed a crossover interaction: low confident recognition hits were slower during recognition but faster during source memory when compared to the opposite pattern seen for instances of high confident hits. Results provide a comprehensive characterization of the individual variability of the FN400 and LPC effects of memory, while adding the behavioral and physiological characterization of a late negative-going ERP effect for accurate source memory without recollection. Conclusions indicated that episodic context could be retrieved independently from recollection, while suggesting a role for a process of context familiarity that is independent from item-familiarity. HighlightsO_LIRecollection is often defined as remembering the source or context of information C_LIO_LIPrior work used ERPs to identify times when source memory did not have recollection C_LIO_LICurrent work replicated ERPs with added response times and measures of variance C_LIO_LIRecollection was not evident in certain source memories, which had a negative ERP C_LIO_LIRecollection is independent of context and is more than just remembering sources C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC="FIGDIR/small/339697v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@4926f8org.highwire.dtl.DTLVardef@9d87d4org.highwire.dtl.DTLVardef@40a701org.highwire.dtl.DTLVardef@9460f1_HPS_FORMAT_FIGEXP M_FIG C_FIG

Brain networks supporting visual memory include extrastriate and other cortical regions associated with visual perception, which manifest domain-specific processing of "where," "how," and various aspects of "what" information. However, whether and how such specialization affects memory for these types of information is still a matter of debate. Functional neuroimaging studies point to dissociable as well as common network components supporting the perception and memory of different aspects of visual information. In the current neuropsychological study, we assess the impact of stroke lesion topography on recall of identity, location, and action of event participants, as assessed by the WMS-III Family Pictures subtest. We used voxel-based lesion-behavior mapping (VLBM) to identify brain lesions specifically implicated in memory deficits for each dimension. Behavioral analysis disclosed impaired performance by both right- and left-hemisphere damage patients, with lesions on each side yielding distinct effects. VLBM analysis revealed a bi-hemispheric network supporting these various aspects of visual memory. In the right hemisphere, the network includes frontal, parietal, and temporal cortical regions and the basal ganglia. In the left hemisphere, the network is more restricted, including visual association areas and medial temporal lobe regions. We further observed that a subset of these regions - those included in the ventral ("what") stream, and in the putative core recollection network - is implicated in multiple aspects of visual memory, whereas other areas are specifically implicated in memory for specific aspects of the visual scene.

Considerable debate surrounds syntactic processing similarities in language and music. Yet few studies have investigated how syntax interacts with meter considering that metrical regularity varies across domains. Furthermore, there are reports on individual differences in syntactic and metrical structure processing in music and language. Thus, a direct comparison of individual variation in syntax and meter processing across domains is warranted. In a behavioral (Experiment 1) and EEG study (Experiment 2), participants engaged in syntactic processing tasks with sentence- and melody stimuli that were more or less metrically regular, and followed a preferred or non-preferred (but correct) syntactic structure. We further employed a range of cognitive diagnostic tests, parametrically indexed verbal- and musical abilities using a principal component analysis, and correlated cognitive factors with the behavioral and ERP results (Experiment 3). Based on previous results in the language domain, we expected that a regular meter would facilitate the syntactic integration of non-preferred syntax. While syntactic discrimination was better in regular than irregular meter conditions in both domains (Experiment 1), a P600 effect indicated different integration costs during the processing of syntactic complexities in the two domains (Experiment 2). Metrical regularity altered the P600 response to preferred syntax in language while it modulated non-preferred syntax processing in music. Moreover, experimental results yielded within-domain individual differences, and identified continuous metrics of musical ability more beneficial than grouping musicians or non-musicians (Experiment 3). These combined results suggest that the meter-syntax interface differs uniquely in how it forms syntactic preferences in language and music.

Understanding how the brain represents meaning at different levels of specificity, from general categories (bird) through combined phrases (nocturnal bird) to specific exemplars (owl), is a central question in semantic cognition and its disorders. The anterior temporal lobes (ATL) have been implicated in both activating stored conceptual representations and combining them, yet whether these two routes to conceptual content engage the ATL in the same way remains an open question. We recorded concurrent MEG-EEG from 36 participants reading 100 conceptual triads varying parametrically in specificity: general words (bird), adjective-noun phrases (nocturnal bird), and specific words (owl). Source analyses revealed a non-linear pattern in bilateral ATL (400-520ms): high-specificity concepts elicited greater activity than both low-specificity words and mid-specificity phrases. Bilateral inferior frontal cortex showed this effect with similar timing (430-630ms). N400 amplitude and ATL source activity showed a functional dissociation in their sensitivity to word frequency, ruling out a purely frequency account of the ATL and IFC effects. Results imply that accessing high-specificity concepts requires individuating stored representations among competitors, whereas phrases construct meaning through a different route. These findings extend the unified semantic hub account by revealing that computational operations within the ATL vary depending on task and stimulus demands.

To effectively function in an ever-changing environment, the brain is proposed to make predictions about upcoming information. However, the association between prediction and memory formation and the role of between-subject neural variability in this relationship is unclear. To shed light on the relationship between prediction and memory, the present study reanalysed data from Jano, Chatburn, and colleagues (2024). In the original experiment, participants were exposed to naturalistic images in predictable and unpredictable four-item sequences, after which their memory was tested using an old/new paradigm. In the present analysis (N = 46), N400 amplitude and oscillatory power during learning was measured to gauge processes related to prediction error and memory encoding, respectively. This activity was compared with subsequent memory outcomes and individual alpha frequency (IAF) calculated at rest. Linear mixed-effects regressions revealed an alpha power subsequent memory effect that was not related to the amplitude of the N400, suggesting that memory encoding may occur independently of the level of prediction error. Notably, IAF influenced the relationship between theta power, N400 amplitude and subsequent memory, implying that the electrophysiological conditions for successful memory formation differ between individuals. Consequently, the degree to which prediction errors (presumably gauged via the N400) drive memory encoding could depend on inter-individual variability in intrinsic neural activity. These findings emphasise the flexible nature of memory, whilst having potential implications for prediction error-driven accounts of learning.

Agrammatic aphasia is an acquired language disorder characterized by slow, non-fluent speech that include primarily content words. It is well-documented that people with agrammatism (PWA) have difficulty with production of verbs and verb morphology, but it is unknown whether these deficits occur at the single word-level, or are the result of a sentence-level impairment. The first aim of this paper is to determine the linguistic level that verb morphology impairments exist at by using magnetoencephalography (MEG) scanning to analyze neural response to two language tasks (one word-level, and one sentence-level). It has also been demonstrated that PWA benefit from a morphosemantic intervention for verb morphology deficits, but it is unknown if this therapy induces neuroplastic changes in the brain. The second aim of this paper is to determine whether or not neuroplastic changes occur after treatment, and explore the neural mechanisms by which this improvement occurs.

The neural basis for the processing of musical syntax has previously been examined almost exclusively in classical tonal music, which is characterized by strictly organized hierarchical structure. The present study investigated the neural mechanisms for processing musical syntax across genres varying in tonality - classical, impressionist, and atonal music - and, in addition, examined how musicianship modulates such processing. Results showed that, first, the dorsal stream, including bilateral inferior frontal gyrus and superior temporal gyrus, plays a key role in the perception of tonality. Second, right fronto-temporal regions were crucial in allowing musicians to outperform non-musicians in musical syntactic processing; musicians also benefit from a cortical-subcortical network including pallidum and cerebellum, suggesting more auditory-motor interaction in musicians than in non-musicians. Third, left pars triangularis carries out on-line computations independently of tonality and musicianship, whereas right pars triangularis is sensitive to tonality and partly dependent on musicianship. Finally, unlike tonal music, processing of atonal music could not be differentiated from that of scrambled notes, both behaviorally and neurally, even among musicians. The present study highlights the importance of studying varying music genres and experience levels, and provides a better understanding of musical syntax and tonality processing and how such processing is modulated by music experience.

Two main types of musical creativity in the western canon are improvisation and interpretation. With improvisation, the fundamental structure of the melody, chords, rhythm and tempo of a piece can be modified, while with interpretation, the focus is on the emotional dynamics. Here we characterise electrical brain activity from professional jazz and classical pianists, whilst they were engaged in these different creative tasks with musical excerpts from both genres. Multivariate EEG was recorded during two phases of each task, mental planning and actual performance. Subsequently neuronal activity patterns were source localised with standardised low resolution electromagnetic tomography (sLORETA). For each musical performance, we obtained both subjective (self-rated) and objective (blind, expert-rated) measures of musical creativity. Across both tasks and genre backgrounds, within the first and middle 4 second segments of the performance phase, for musical performances that were judged highly creative objectively by external expert music assessors, we observed an increased activation in the anterior cingulate and medial prefrontal cortex (Brodmann area, BA32), suggesting a maintenance of executive control, and integrating motoric and emotional communication during creativity. Across genre backgrounds, within the performance phase for the interpretation task compared to the improvisation task, there was an increased activity in the insula (BA 13), suggesting a convergent creative task from the linked goal-orientated conscious error-monitoring and audio-visual integration functions. Genre profession also gave rise to differences across phases; jazz pianists presented a decreased parietal (BA7) activity during improvisation tasks suggesting a role for defocussed attention and for classical pianists, both tasks were associated with occipitotemporal (BA 37) activity which is involved in semantic/ metaphorical processing suggesting a close adherence to the visual score. These 3 areas relate the cognitive demands of the creative musical task to the demands of the corresponding genre of music. HighlightsO_LIEEG activity associated to musical creativity types: Improvisation and Interpretation C_LIO_LIIncreased activity in Insula (BA 13) for Interpretation suggest convergent creativity C_LIO_LIDecreased Precuneus (BA7) activity for Improvisation suggest defocussed attention C_LIO_LIIncreased activity in medial prefrontal cortex (BA32) in highly creative performance C_LI

Primary progressive aphasia (PPA) is a neurodegenerative syndrome characterized by progressive language deficits. There are three main variants of PPA - semantic (svPPA), logopenic (lvPPA), and nonfluent (nfvPPA) - that can be challenging to distinguish. Limb praxis may also be affected in PPA, but it is unclear whether different variants of PPA are associated with differences in gesture production. Prior research with neurotypical individuals indicates that the left temporal lobe is a critical locus of manipulable object and hand posture representations. Moreover, when imitating gestures, individuals whose strokes include the left temporal lobe show reduced benefit of gesture meaning and disproportionate impairment in hand posture as compared to arm kinematics. We tested the hypothesis that svPPA - who typically exhibit primarily temporal lobe atrophy - would differentially show these expected patterns of gesture imitation performance. Nineteen participants with PPA completed meaningful and meaningless gesture imitation tasks, and performance was scored for hand posture and arm kinematics accuracy. Generalized logistic mixed-effect regression models controlling for dementia severity showed overall benefits from gesture meaning, and greater impairments in hand posture than arm kinematics. We also found that svPPA participants were the most impaired in gesture imitation overall. Critically, there was also a significant three-way interaction of group, meaning, and gesture component: only svPPA participants showed relative impairments of hand posture for meaningful gestures as well as meaningless gestures. Thus, unlike lvPPA and nfvPPA, the hand postures of svPPA failed to benefit from gesture meaning. This research extends prior findings on the role of the temporal lobe in hand posture representations associated with manipulable objects, and is the first to indicate that there may be distinct gesture imitation patterns as a function of PPA variant. Characterizing componential gesture deficits in PPA may help to inform differential diagnosis, compensatory communication strategies, and cognitive praxis models of PPA.

Anterior lateral prefrontal cortex (aLPFC) has been consistently implicated in retrieval monitoring and relational reasoning. However, it is unknown whether aLPFC supports a cognitive process that is common to memory retrieval and reasoning tasks. To inform this question, a first step is to ascertain whether there is, within individuals, spatial overlap in aLPFC between tasks. A prior study found overlap in activation of left aLPFC between verbal analogy and source memory retrieval tasks, using tightly matched word stimuli (Westphal et al., 2016). To assess whether this overlap in activation extends to other stimulus types and task designs, and another sensory modality, we collected fMRI data from 35 healthy young adults as they completed an associative memory retrieval task along with four variants of a relational reasoning paradigm that reliably engages left aLPFC. The reasoning tasks followed a 2 (visual/auditory modality) x 2 (spatial/featural relations) x 2 (low/high relational complexity) design. In the associative memory task, participants studied word pairs and decided whether the two words were related. At retrieval, they viewed pairs of previously seen words and judged whether the pair was Intact (words paired together at encoding) or Recombined (previously seen words recombined into new pairs). Response times were slower for Recombined vs. Intact pairs, consistent with heightened retrieval monitoring. As predicted, aLPFC was more active for Recombined than Intact pairs, as well as for the manipulation of relational complexity across the four reasoning tasks. A group-level conjunction analysis demonstrated substantial overlap between memory and reasoning manipulations in left aLPFC (Glasser parcels a47r, p47r, a10p, and p10p). Within individuals, clusters defined from the reasoning task were also sensitive to retrieval monitoring demands. Further, there was within-participant overlap in the pattern of active vertices, as measured via Dice coefficients. Bayes factor testing within each parcel of interest demonstrated greater vertex-level overlap than expected by chance, particularly in p47r. Importantly, degree of overlap varied widely among individuals, and exploratory results showed that both cluster-level activation and vertex overlap in p47r correlated with memory discriminability (d-prime). Thus, we hypothesize that neural overlap in this area reflects engagement in relational thinking during memory retrieval monitoring. Together, these results move beyond general characterizations of aLPFC function by testing whether it meets a precondition -- individual-level neural overlap across varied tasks -- of a unified neurocognitive function in support of reasoning and memory retrieval.