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Neuronal selectivity and invariance
Neuronal selectivity and invariance
Decoding
visual inputs from multiple neurons in the human temporal lobe
R. Q.
Quiroga, L. Reddy, C. Koch & I. Fried
Journal of Neurophysiology, 98,
2007, pp. 1997-2007, doi:10.1152/jn00125.2007
http://jn.physiology.org/
This
study involved the simultaneous recording of numbers of single neurons in the
human medial temporal lobe. The medial temporal lobe receives projections from
the inferior temporal lobe which is regarded as the area involved in the final
stage of purely visual processing. Individual neurons in the medial temporal
were shown to respond to images of particular people, animals or landmarks. Those
cells that did fire had a sharp increase in their firing, and continued to fire
after the stimulus had ceased. About one third of these responsive neurons were
activated by differing views of particular individuals or objects, or even in
some cases written forms of their name. The experimenters demonstrated that
they could make an above chance prediction of which of a range of images had
been projected to the subject, just on the basis of which neurons had spiked.
The responses of the medial temporal neurons were very selective, with each
neuron firing in response to only a few of the pictures presented. Thus only
3.3% of images presented produced any response, cells firing in response to
between one and four out of a total of 114 pictures shown. In some trials,
subjects saw between three and eight different views of individuals or objects,
and these trials demonstrated that some cells were invariant in the sense that
they fired selectively for a different views of the same object, including the
object shown in a drawing or as a word.
The data here is considered to be
consistent with the identity of particular individuals or objects being
represented by only a small number of neurons, and this representation being
invariant in the sense of functioning for many different views of the object. This
study emphasises the importance of single neurons in conscious experience,
although it does not negate the evidence for a strong correlation between the
global gamma synchrony and consciousness.
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