The long-term goal of the proposed studies is to understand the cortical mechanisms that mediate the memory of tactile characteristics of objects. The focus of the research is to test the hypothesis that primary somatosensory cortex (SI) and secondary somatosensory cortex (SII) participate in working memory of tactile stimuli and non-tactile (visual) stimuli that by experience have been associated with the tactile stimuli. Monkeys will be trained to perform the tactile-tactile unimodal and the visual-tactile cross-modal working memory tasks. In those tasks, the presentation of tactile or visual cues is followed by a delay period (10-20 seconds). At the end of the delay, by manual grasp the animal makes the choice of objects determined by the preceding cues. Cellular discharge will be recorded in SI as well as SII when the fully trained animal is performing the tasks. The multi-microelectrode methods will be used for recording. The records will be analyzed to reveal changes in cellular activity correlated with the short-term retention of those tactile or visual cues. Activities of cells in SI and SII recorded in the unimodal task will be compared with those recorded in the cross-modal task. The overall similarities and differences in the activity of cells between SI and SII in a same hemisphere will be examined. The results of this study are expected to clarify the cortical neurobiology engaged in the cognitive aspects of sensory information processing, sensorimotor integration, and learning and memory. Thus, this research project has clear implications for understanding the development of cognitive functions, the recovery of cognitive functions from brain injuries (stroke, trauma), and the neurobiology of both normal and pathological aging in the human.
