Medial entorhinal-hippocampal desynchronization parallels the emergence of memory impairment in a mouse model of Alzheimer's disease pathology

Alzheimers disease (AD) is a neurodegenerative disease characterized by progressive impairments in episodic and spatial memory, as well as circuit and network-level dysfunction. While functional impairments in medial entorhinal cortex (MEC) and hippocampus (HPC) have been observed in patients and rodent models of AD, it remains unclear how communication between these regions breaks down in disease, and what specific physiological changes are associated with the onset of memory impairment. We used silicon probes to simultaneously record neural activity in MEC and hippocampus before or after the onset of spatial memory impairment in the 3xTg mouse model of AD pathology. We found that reduced hippocampal theta power, reduced MEC-CA1 theta coherence, and altered phase locking of MEC and hippocampal neurons all coincided with the emergence of spatial memory impairment in 3xTg mice. Together, these findings indicate that disrupted temporal coordination of neural activity in the MEC-hippocampal system parallels the emergence of memory impairment in a model of AD pathology. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC="FIGDIR/small/633171v1_ufig1.gif" ALT="Figure 1"> View larger version (58K): org.highwire.dtl.DTLVardef@11606a5org.highwire.dtl.DTLVardef@10e5d0borg.highwire.dtl.DTLVardef@1feabe1org.highwire.dtl.DTLVardef@c646ed_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGRAPHICAL ABSTRACTC_FLOATNO C_FIG HighlightsO_LISpatial memory impairments in 3xTg mice emerge between 6 and 8 months of age C_LIO_LIMemory deficits emerge alongside reduced HPC theta power and reduced CA1-MEC theta coherence C_LIO_LIMemory deficits emerge alongside disrupted timing of MEC and HPC neural activity C_LIO_LIInterneuron loss in MEC and interneuron desynchronization in HPC occur prior to memory impairment C_LI