Impaired allocentric spatial working memory and intact retrograde memory after thalamic damage caused by thiamine deficiency in rats

Rats were tested on an allocentric-spatial working-memory task-delayed matc hing-to-place (DMTP) in a water maze-before and after either pyrithiamine-i nduced thiamine deficiency (PTD) or electrolytic lesions of the lateral int ernal medullary laminae (IML), an area damaged by PTD. DMTP trials consiste d of paired swims, with the escape platform in a new location on each trial . PTD rats were impaired at retention delays of 300 s, but not at delays of 4 or 60 s. Rats with IML lesions performed normally at all delays. Both gr oups displayed normal retention of object-discrimination problems that they had learned at different intervals before treatment (5 weeks, 3 weeks, and 1 week). The results suggest that PTD causes delay-dependent deficits of a llocentric spatial working memory and that damage outside the IML is probab ly responsible. Neither PTD-induced diencephalic damage nor restricted IML lesions appear to produce a global retrograde amnesia.