Cerebral Cortex Advance Access published online on May 9, 2008
Cerebral Cortex, doi:10.1093/cercor/bhn071
The Roles of Human Lateral Temporal Cortical Neuronal Activity in Recent Verbal Memory Encoding
1 Department of Neurological Surgery, 2 Department of Psychology, University of Washington, Seattle, WA 98195, USA
Address correspondence to George A. Ojemann, MD, Department of Neurological Surgery, Campus Box 356470, University of Washington, 1959 Northeast Pacific Street, Seattle, WA 98195, USA. Email: gojemann{at}u.washington.edu
Activity of 98 single neurons in human lateral temporal cortex was measured during memory encoding for auditory words, text, or pictures and compared with identification of material of the same modality in extracellular recordings during awake neurosurgery for epilepsy. Frequency of activity was divided into early or late epochs or activity sustained throughout both; 44 neurons had significant changes in one or more categories. Polymodal and sustained changes lateralized to dominant hemisphere and late changes to nondominant. The majority of polymodal neurons shifted categories for different modalities. In dominant hemisphere, the timing and nature of changes in activity provide the basis for a model of the roles of temporal cortex in encoding. Superior temporal gyrus excitatory activity was related to the early epoch, when perception and processing occur, and middle gyrus to the late epoch, when semantic labeling occurs. The superior two-thirds of middle gyrus also demonstrated sustained inhibition. In a subset of lateral temporal neurons, memory-encoding activity reflected simultaneous convergence of sustained attentional and early perceptual inputs.
Key Words: cortex and thalamus • learning and memory • physiology
3 Current address: Department of Psychology, Center for Mind and Brain, University of California, Davis, CA 95618, USA