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Abstract:
Abstract: We studied the visual properties of single neurons
in the temporal lobe of patients with intractable epilepsy. Based
on clinical criteria, intracranial electrodes were implanted to
localize seizure foci for surgical resection. Probes were
stereotactically placed in bilateral medial temporal lobe targets
including hippocampus, amygdala, entorhinal cortex and
parahippocampal gyrus. We recorded the activity of individual
neurons while patients viewed pictures of faces, objects, patterns
and animals on a monitor and when the patients were asked to
imagine these pictures with closed eyes. Two pictures, A and B,
were presented in random alternation, 5 times each, 1000 ms per
presentation. Immediately after this, subjects were asked to close
their eyes and imagine stimulus A upon hearing a high tone and
stimulus B upon hearing a low tone. Tones alternated every 3000 ms.
We analyzed activity from 248 neurons in 10 epileptic patients.
58/248 neurons showed visual responses and 31/248 neurons showed
selective visual responses. Most of the visually responsive neurons
were located in the hippocampus and entorhinal cortex. We analyzed
activity during visual imagery in 163 neurons.13/163 neurons showed
selective changes in firing rates while subjects had to visually
recall the same stimuli. Our preliminary results suggest that
neurons in the temporal lobe may be involved in the generation or
maintenance of visual images in our minds in the absence of retinal
stimulation.
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