The Journal of Neuroscience, July 1, 1999, 19(13):5674-5682
Activity of Neurons in Human Temporal Cortex during
Identification and Memory for Names and Words
George A.
Ojemann and
Julie
Schoenfield-McNeill
Department of Neurological Surgery, University of Washington,
Seattle, Washington, 98195
Extracellular recordings of human temporal cortical neuronal
activity during identification and memory for object names or words
were obtained from 31 neurons at 18 sites in 12 left language dominant
patients undergoing left (10) or right (2) awake craniotomy for
epilepsy under local anesthesia. Frequency of activity during identification was compared with perceptual controls, that during the
encoding phase of recent memory to identification of the same material.
Statistically significant changes in one or more temporal epoch
(p < 0.005) of one or more comparisons were
present for 27 of the 31 neurons in either hemisphere. Few neurons
changed activity in the same direction for both words and names. The
instruction to retain an item in recent memory changed activity in most
neurons from that during identification of the same material, although the items presented were identical and overtly identified in each task.
Any individual neuron usually changed activity in one direction for
only one task. There are separate, widely distributed neural networks
for identification or recent memory for each type of material. The
majority of nearby neurons recorded through the same extracellular
microelectrode were related to the networks for different tasks.
The temporal characteristics of these changes were also investigated;
31% of the changes were "phasic": temporally related to
presentation or response to the item. Most of the remaining neuron
changes were sustained throughout a task, often for several minutes.
These task-specific sustained changes may reflect effects of
thalamo-cortical attentional systems. Individual neurons had both
sustained and phasic changes to different tasks.
Key words:
human; neuron; temporal; cortex; memory; language
Copyright © 1999 Society for Neuroscience 0270-6474/99/19135674-09$05.00/0