Single Neuron Coding of Identity in the Human Hippocampal Formation

REY, HERNAN G.; GORI, BELEN; CHAURE, FERNANDO J.; COLLAVINI, SANTIAGO; BLENKMANN, ALEJANDRO O.; SEOANE, PABLO; SEOANE, EDUARDO; KOCHEN, SILVIA; QUIAN QUIROGA, RODRIGO

CURRENT BIOLOGY

CELL PRESS

Año: 2020 vol. 30 p. 1152 - 1159

0960-9822

Experimental findings show the ubiquitous presenceof graded responses and tuning curves in theneocortex, particularly in visual areas [1?15]. Amongthese, inferotemporal-cortex (IT) neurons respond tocomplex visual stimuli, but differences in the neu-rons? responses can be used to distinguish thestimuli eliciting the responses [8, 9, 16?18]. The ITprojects directly to the medial temporal lobe (MTL)[19], where neurons respond selectively to differentpictures of specific persons and even to their writtenand spoken names [20?22]. However, it is not clearwhether this is done through a graded coding, as inthe neocortex, or a truly invariant code, in which theresponse-eliciting stimuli cannot be distinguishedfrom each other. To address this issue, we recordedsingle neurons during the repeated presentation ofdifferent stimuli (pictures and written and spokennames) corresponding to the same persons. Usingstatistical tests and a decoding approach, we foundthat only in a minority of cases can the different pic-tures of a given person be distinguished from theneurons? responses and that in a larger proportionof cases, the responses to the pictures were differentto the ones to the written and spoken names. Weargue that MTL neurons tend to lack a representationof sensory features (particularly within a sensory mo-dality), which can be advantageous for the memoryfunction attributed to this area [23?25], and that afull representation of memories is given by a combi-nation of mostly invariant coding in the MTL with arepresentation of sensory features in the neocortex.