Biology subjects

Jannuzi, B. G. L.

Publications and source records attributed to Jannuzi, B. G. L..

3 recordsLinked to original sources

bioRxiv2025

Resolving a paradox about how vision is transformed into familiarity

How is the act of seeing an image transformed into the memory that it has been seen? To investigate, we leveraged the systematic variation with which some images are better remembered than others, image memorability, to compare neural responses in inferotemporal cortex (ITC) and the hippocampus (HC) as macaque monkeys performed a single-exposure visual familiarity task. We found evidence for a two-stage algorithmic transformation from visual representations to familiarity, including a previously undescribed computational transformation of familiarity in the medial temporal lobe. At the first stage, more memorable images elicited more vigorous ITC firing-rate responses and stronger ITC familiarity signals (reflected as repetition suppression). This led to a counterintuitive intermingling of familiarity and memorability signals in ITC, but a representation that could be read out by a linear decoder. At the next stage, the medial temporal lobe selectively extracted ITC familiarity signals to produce a more isolated familiarity representation with minimal memorability modulation, reflected downstream in HC. These results shed light on how seeing is transformed into familiarity, and they establish the existence of a previously undescribed medial temporal lobe computation.

neuroscience↗

bioRxiv2025

Sharpened visual memory representations are reflected in inferotemporal cortex

Humans and other primates can robustly report whether theyve seen specific images before, even when those images are extremely similar to ones theyve previously seen. Multiple lines of evidence suggest that pattern separation computations in the hippocampus (HC) contribute to this behavior by shaping the fidelity of visual memory. However, unclear is whether HC uniquely determines memory fidelity or whether computations in other brain areas also contribute. To investigate, we recorded neural signals from inferotemporal cortex (ITC) and HC of two rhesus monkeys as they performed a memory task in which they judged whether images were novel or exactly repeated in the presence of visually similar lure images with a range of visual similarities. We found behavioral evidence for sharpening, reflected as memory performance that was nonlinearly transformed relative to a benchmark defined by visual representations in ITC. As expected, we found that behavioral sharpening aligned with visual memory representations in HC. Surprisingly, and unaccounted for by HC pattern separation proposals, we also found neural correlates of behavioral sharpening reflected in ITC. These results, coupled with further analysis of the data, suggest that ITC contributes to shaping the fidelity of visual memory in the transformation from visual processing to memory storage and signaling. SignificanceVisual recognition memories are stored with remarkable visual fidelity, allowing humans and other primates to distinguish images they have encountered from visually similar images they have not. This fidelity has long been attributed to computations in the hippocampus that sharpen visual representations before memory storage ("pattern separation"). Unclear is how this proposal aligns with other evidence that visual memories are stored within high-level visual cortex itself, before signals reach the hippocampus. Here we demonstrate that, like the hippocampus, inferotemporal cortex also reflects sharpened visual memory representations, suggesting that visual cortex contributes to shaping the visual fidelity of visual memory.

neuroscience↗

bioRxiv2019

Normative Data for an Expanded Set of Stimuli for Testing High-Level Influences on Object Perception: OMEFA-II

We present normative data for bipartite displays used to investigate high-level contributions to object perception in general and to figure-ground perception in particular. In these vertically-elongated displays, two equal-area regions of different luminance abut a central, articulated, vertical border. In Intact displays, a portion of a mono-oriented well-known (\"familiar\") object is sketched along one side of the border; henceforth the \"critical side.\" The other side is the \"complementary side.\" We measured inter-subject agreement among 32 participants regarding objects depicted on the critical and complementary sides of the borders of Intact displays and two other types of displays: upright and inverted Part-Rearranged displays. The parts on the critical side of the border are the same in upright Intact and Part-Rearranged displays but spatially rearranged into a new configuration in the latter. Inter-subject agreement is taken to index the extent to which a side activates traces of previously seen objects near the central border. We report normative data for 288 regions near the central borders of 144 displays (48/type) and a thorough description of the image features. This set of stimuli is larger than an older \"Object Memory Effects on Figure Assignment\" (OMEFA) set. This new OMEFA-II set of high-resolution displays is available online (https://osf.io/j9kz2/).

neuroscience↗