Effects of entorhinal cortex lesions on sensory integration and spatial learning

Background: The entorhinal cortex provides sensory information to the hippo campus for memory and learning. Damage to the entorhinal cortex is common i n patients who experience traumatic brain injury, stroke, and Alzheimer's d isease. Entorhinal damage is assumed to interfere with sensory integration; however, substantive knowledge of behavioral patterns is lacking. Objectives: To describe specific behavioral deficits associated with entorh inal cortex injury related to special senses identification, sensory integr ation, and spatial learning. Method: Adult male rats received bilateral entorhinal cortex damage (n = 19 ) or sham surgery (n = 11)with a subset randomized to participate in specia l senses identification, exploration, and sensory integration testing. Spat ial learning was examined using a water maze. Results: Lesion and control animals were similar in special senses identifi cation testing. Sensory integration was markedly impaired in lesion animals over 3 days for all integration tasks; however, travel deficit persisted f or 4 days. By day 5 sensory integration ability was equal. Lesion animals w ere significantly impaired across all days of spatial learning for swim tim e (p = .0001) and directional heading error (p = .03). Control animals expo sed to sensory testing demonstrated significantly more efficient learning ( p = .005) on swim days 2 and 3 versus control animals not exposed to sensor y testing. Conclusions: Early and prolonged behavioral changes are evident following e ntorhinal cortex damage including sensory integration deficits and persiste nt spatial learning impairment.