Squirrels, Memory and Plasticity
So nice to see everyone so nuts about squirrels at Harvard! Colleen Walsh and I talked squirrels for over an hour and here is her excellent summary of some of the highlights.
She was particularly interested in the question of memory and hippocampal plasticity. Speculative on my part, of course, though not without considerable thought on the question; Bruce Miller (UCSF), Stephanie Preston (Univ Michigan) and I worked for over a year on this, brainstorming and piloting memory tasks for Alzheimer and fronto-temporal dementia patients, inspired by our squirrel data. Anna Waismeyer (then Waisman, recently moved to Microsoft) and I continued this discussion in 2008 (excerpt below). So it’s not inconceivable that understanding the squirrel’s ‘cache brain’ plasticity could lead to therapeutic innovations for neurodegenerative disease.
“This pattern of results is also consistent with known seasonal changes in the brain of a congener species, the eastern gray squirrel (S. carolinensis). Adult male squirrels showed a signifcant increase in brain size in October, the height of the caching season, compared to adult squirrels captured in January or June (Lavenex et al. 2000). There was also an absolute increase in the hippocampal subWeld (CA1), a structure selectively active during the encoding of small unique objects in the lab rat (Kemp and Manahan-Vaughan 2007, 2008). Thus, the male fox squirrel’s greater attendance to unique featural cues in the late summer may be related to seasonal changes in how its hippocampus encodes a location. In addition, such a dissociation of hippocampal functions by cue class is consistent with the parallel map model of spatial encoding (Jacobs and Schenk 2003). “