Effects of Familiarity on Neural Activity in Monkey Inferior Temporal Lobe

Abstract

Long-term familiarity facilitates recognition of visual stimuli. To better understand the neural basis for this effect, we measured the local field potential (LFP) and multiunit spiking activity (MUA) from the inferior temporal (IT) lobe of behaving monkeys in response to novel and familiar images. In general, familiar images evoked larger amplitude LFPs whereas MUA responses were greater for novel images. Familiarity effects were attenuated by image rotations in the picture plane of 45 degrees. Decreasing image contrast led to more pronounced decreases in LFP response magnitude for novel, compared with familiar images, and resulted in more selective MUA response profiles for familiar images. The shape of individual LFP traces could be used for stimulus classification, and classification performance was better for the familiar image category. Recording the visual and auditory evoked LFP at multiple depths showed significant alterations in LFP morphology with distance changes of 2 mm. In summary, IT cortex shows local processing differences for familiar and novel images at a time scale and in a manner consistent with the observed behavioral advantage for classifying familiar images and rapidly detecting novel stimuli.

Statistical learning of visual transitions in monkey inferotemporal cortex

“…We then took the difference between the maximum and minimum as the amplitude of the response. The peak-to-peak amplitude measured in these experiments was lower than in most other published studies (59,60). This discrepancy is irrelevant to all statistical comparisons because they concern the relative rather than the absolute amplitude of the response.…”

High-resolution imaging of the fusiform face area (FFA) using multivariate non-linear classifiers shows diagnosticity for non-face categories

“…The literature on visual expertise of non-face categories in macaques is limited by comparison in its relation to face specificity, yet the general findings still cast doubt on the traditional interpretation of face-selective modules. Studies in the macaque inferotemporal cortex show that area TE develops stronger selectivity after familiarization/training on complex images; this selectivity increase has been observed in singleunit recordings of training images over distractors (Logothetis et al, 1995), single-unit recordings of trained over untrained monkeys (Kobatake et al, 1998), and of LFP and multi-unit activity (MUA) of familiar over novel images (Anderson et al, 2008). Given the drastic increase in selectivity after a few months of training, it is a strong possibility that a face module simply reflects a much higher level of visual expertise for faces, for which monkeys (and humans) have years of training.…”

Stimulus selectivity and response latency in putative inhibitory and excitatory neurons of the primate inferior temporal cortex

“…Importantly, these functional differences were apparent during self-guided exploration through complex visual displays, suggesting that they are relevant for natural vision. Additional studies will be useful for understanding how other fundamental neuronal properties, such as receptive field structure (Op De Beeck and Vogels 2000) and experience-dependent plasticity (Anderson et al 2008;Freedman et al 2006;Woloszyn and Sheinberg 2012), vary across cell type. Such comparisons will be critical for developing biologically plausible models of visual processing that take into account the role of different cell types.…”