Inferotemporal Research Articles

The Corneal Epithelial Thickness Profile in a Healthy Saudi Population.

Epithelial mapping appears to be a valuable technique for acorneal and refractive surgeon, useful for distinguishing corneas with the true presence of corneal ectasia from those that are suspicious.Interpreting the epithelial thickness map data requires an understanding of corneal epithelial thickness (CET) normal values and variable patterns. Unlike corneal thickness, epithelial thickness assessment with anterior segment optical coherence tomography (AS-OCT) seems to be influenced by gender and age. The study aimed to investigate the detailed mapping of CETcharacteristics in normal eyes from the Saudi population and to assess its variation with age and sex using anterior segment 7-mm-wide OCT (AS-OCT) scans. Regional epithelial thickness was assessed using an anterior radial scanning protocol with REVO NX (Optopol Technology S.A, Zawiercie, Poland) in 596 eyes of 298 individuals aged 10 to 98. CET maps in a 7 mm diameter wereautomatically generated by the built-in software, displaying thickness in 17 sectors divided into three zones, i) a central zone within the 0-2 mm diameter, ii) ring 1 zone, a paracentral (P-CET) zone from 2 to 5-mm, and iii) ring 2 zone, a midperipheral zone (MP-CET) from 5 to 7 mm. Ring 1 and 2 zones were further divided into eight sectors each, including superior (S), inferior (I), nasal (N), temporal (T), superonasal (SN), inferonasal (IN), superotemporal (ST), and inferotemporal (IT). An analysis was done on correlations between age and gender and the CET across different zones. Males and older adults had a substantially thicker CET than females and younger participants, with the C-CET measuring 59.2±4.5µm. In three zones, no interocular asymmetry was seen. Superiorly, CET is significantly thinner than inferiorly (p<0.05), with temporal zones being thinner than nasal zones (p<0.05). The C-CET increases with age in the seven groups of both genders, but its dependence on age is weaker in paracentral sectors; C-CET was 3.5% thicker in males. Paracentral nasal and inferior zones showed 2.2-3.6% thicker CET while the superior and temporal paracentral zones showed 3-5% thicker CET among males compared to females. From 17 CET zones of central 7 mm cornea the C-CET was affected by gender and age.The CET distribution in these healthy Saudis' eyes was non-uniform with the CET being thinner in the superior cornea.This finding could aid in predicting corneal diseases and planning refractive procedures.

Behavioral and Neural Mechanisms of Face-Specific Attention during Goal-Directed Visual Search.

Goal-directed visual attention is a fundamental cognitive process that enables animals to selectively focus on specific regions of the visual field while filtering out irrelevant information. However, given the domain specificity of social behaviors, it remains unclear whether attention to faces versus nonfaces recruits different neurocognitive processes. In this study, we simultaneously recorded activity from temporal and frontal nodes of the attention network while macaques performed a goal-directed visual search task. V4 and inferotemporal (IT) visual category-selective units, selected during cue presentation, discriminated fixations on targets and distractors during the search but were differentially engaged by face and house targets. V4 and IT category-selective units also encoded fixation transitions and search dynamics. Compared with distractors, fixations on targets reduced spike-LFP coherence within the temporal cortex. Importantly, target-induced desynchronization between the temporal and prefrontal cortices was only evident for face targets, suggesting that attention to faces differentially engaged the prefrontal cortex. We further revealed bidirectional theta influence between the temporal and prefrontal cortices using Granger causality, which was again disproportionate for faces. Finally, we showed that the search became more efficient with increasing target-induced desynchronization. Together, our results suggest domain specificity for attending to faces and an intricate interplay between visual attention and social processing neural networks.

Behavioral and neural mechanisms of face-specific attention during goal-directed visual search.

Goal-directed visual attention is a fundamental cognitive process that enables animals to selectively focus on specific regions of the visual field while filtering out irrelevant information. However, given the domain specificity of social behaviors, it remains unclear whether attention to faces versus non-faces recruits different neurocognitive processes. In this study, we simultaneously recorded activity from temporal and frontal nodes of the attention network while macaques performed a goal-directed visual search task. V4 and inferotemporal (IT) visual category-selective units, selected during cue presentation, discriminated fixations on targets and distractors during the search, but were differentially engaged by face and house targets. V4 and IT category-selective units also encoded fixation transitions and search dynamics. Compared to distractors, fixations on targets reduced spike-LFP coherence within the temporal cortex. Importantly, target-induced desynchronization between the temporal and prefrontal cortices was only evident for face targets, suggesting that attention to faces differentially engaged the prefrontal cortex. We further revealed bidirectional theta influence between the temporal and prefrontal cortices using Granger causality, which was again disproportionate for faces. Finally, we showed that the search became more efficient with increasing target-induced desynchronization. Together, our results suggest domain specificity for attending to faces and an intricate interplay between visual attention and social processing neural networks.

Modified "C" Haptic Intraocular Lens Orientation and Negative Dysphotopsia.

Phacoemulsification is the standard of care in cataract surgery in the developed world, with patients having high expectations regarding visual results. Postoperative dissatisfaction due to negative dysphotopsia (ND) ranges from rare to very frequent; its etiology is unclear, and it affects postoperative satisfaction. Since one of the most frequently used strategies to avoid ND is related to intraocular lens (IOL) haptic orientation, we conducted a prospective interventional study that enrolled 197 patients who underwent standard phacoemulsification. All patients had a one-piece hydrophobic acrylic IOL implanted; in one group, the haptics were placed in any meridional axis except inferotemporal (IT) meridians, and in the other group, the IOL was implanted with the haptics in an IT position. Our results showed no statistically significant differences between groups when analyzing the correlation between the position of IOL haptics and the presence of ND in week one and month one. Also, pupillary diameter showed no statistically significant differences between patients with or without ND. Despite some studies claiming that haptic orientation prevents ND, we found that haptic orientation does not correlate with ND incidence and that ND decreases from day 1 to month 1. Our results support previous findings on the decrease in ND over time and that haptic orientation should not be considered an intraoperative strategy to avoid this unwanted phenomenon.

Temporal multiplexing of perception and memory codes in IT cortex

A central assumption of neuroscience is that long-term memories are represented by the same brain areas that encode sensory stimuli1. Neurons in inferotemporal (IT) cortex represent the sensory percept of visual objects using a distributed axis code2–4. Whether and how the same IT neural population represents the long-term memory of visual objects remains unclear. Here we examined how familiar faces are encoded in the IT anterior medial face patch (AM), perirhinal face patch (PR) and temporal pole face patch (TP). In AM and PR we observed that the encoding axis for familiar faces is rotated relative to that for unfamiliar faces at long latency; in TP this memory-related rotation was much weaker. Contrary to previous claims, the relative response magnitude to familiar versus unfamiliar faces was not a stable indicator of familiarity in any patch5–11. The mechanism underlying the memory-related axis change is likely intrinsic to IT cortex, because inactivation of PR did not affect axis change dynamics in AM. Overall, our results suggest that memories of familiar faces are represented in AM and perirhinal cortex by a distinct long-latency code, explaining how the same cell population can encode both the percept and memory of faces.

Perceptography unveils the causal contribution of inferior temporal cortex to visual perception

Neurons in the inferotemporal (IT) cortex respond selectively to complex visual features, implying their role in object perception. However, perception is subjective and cannot be read out from neural responses; thus, bridging the causal gap between neural activity and perception demands independent characterization of perception. Historically, though, the complexity of the perceptual alterations induced by artificial stimulation of IT cortex has rendered them impossible to quantify. To address this old problem, we tasked male macaque monkeys to detect and report optical impulses delivered to their IT cortex. Combining machine learning with high-throughput behavioral optogenetics, we generated complex and highly specific images that were hard for the animal to distinguish from the state of being cortically stimulated. These images, named “perceptograms” for the first time, reveal and depict the contents of the complex hallucinatory percepts induced by local neural perturbation in IT cortex. Furthermore, we found that the nature and magnitude of these hallucinations highly depend on concurrent visual input, stimulation location, and intensity. Objective characterization of stimulation-induced perceptual events opens the door to developing a mechanistic theory of visual perception. Further, it enables us to make better visual prosthetic devices and gain a greater understanding of visual hallucinations in mental disorders.

Clinical Characteristics and Associated Factors to the Development of Glaucoma in Eyes With Myopic Optic Neuropathy

PurposeTo observe the development of glaucoma in myopic eyes with and without myopic optic neuropathy (MON) and analyze associated factors to the development of typical glaucomatous damage. DesignA prospective, observational, cohort study MethodsA total of 233 myopic eyes with no definite evidence of glaucomatous damage were included in the study. Myopic patients without any retinal nerve fiber layer (RNFL) or visual field (VF) abnormalities were classified as myopic eyes without MON. Myopic patients with decreased RNFL at the superonasal (SN) or nasal area, and with corresponding VF defects either in the temporal or inferotemporal (IT) region, which is different from glaucomatous damage, were classified as myopic eyes with MON. Myopic eyes that developed glaucoma were defined by the presence of glaucomatous VF in the SN region including defects in Bjerrum area, or a new localized RNFL defect in the IT region on red-free photography or RNFL OCT. Disc morphological features and optic nerve head (ONH) parameters of two groups were compared. Hazard ratios for the association between baseline factors and conversion to glaucoma were obtained using Cox regression analysis. ResultsMean follow-up period was 11.66 ± 2.86 years. Myopic eyes with MON had a thinner average peripapillary RNFL thickness (P < 0.001), worse MD of the VF (P = 0.031), a higher percentage of IT VF defects (P < 0.001), smaller torsion degree (P = 0.047), and greater LCD (P = 0.022). Myopic eyes with MON who developed glaucoma had a thinner average peripapillary RNFL thickness (P = 0.009), greater PPA area (P = 0.049), greater LCD (P < 0.001), and thinner LCT (P < 0.001). Thinner baseline temporal RNFL thickness (HR, 0.956; 95% CI, 0.928–0.986; P = 0.004), greater baseline LCD (HR, 1.003; 95% CI, 1.000–1.005; P = 0.022), and greater PPA area (HR, 1.000; 95% CI, 1.000–1.003; P = 0.050) were significantly associated factors with glaucoma development in the Cox regression analysis. ConclusionMyopic eyes with MON have a greater risk to develop glaucoma compared to myopic eyes without MON. Myopic eyes with MON had larger PPA area, greater LCD, and thinner temporal peripapillary RNFL, indicating that accompanying structural weakness due to myopia, especially at the temporal side of the optic nerve head and the peripapillary sclera, increases the risk of glaucoma in myopic eyes with MON.

Object recognition in primates: what can early visual areas contribute?

If neuroscientists were asked which brain area is responsible for object recognition in primates, most would probably answer infero-temporal (IT) cortex. While IT is likely responsible for fine discriminations, and it is accordingly dominated by foveal visual inputs, there is more to object recognition than fine discrimination. Importantly, foveation of an object of interest usually requires recognizing, with reasonable confidence, its presence in the periphery. Arguably, IT plays a secondary role in such peripheral recognition, and other visual areas might instead be more critical. To investigate how signals carried by early visual processing areas (such as LGN and V1) could be used for object recognition in the periphery, we focused here on the task of distinguishing faces from non-faces. We tested how sensitive various models were to nuisance parameters, such as changes in scale and orientation of the image, and the type of image background. We found that a model of V1 simple or complex cells could provide quite reliable information, resulting in performance better than 80% in realistic scenarios. An LGN model performed considerably worse. Because peripheral recognition is both crucial to enable fine recognition (by bringing an object of interest on the fovea), and probably sufficient to account for a considerable fraction of our daily recognition-guided behavior, we think that the current focus on area IT and foveal processing is too narrow. We propose that rather than a hierarchical system with IT-like properties as its primary aim, object recognition should be seen as a parallel process, with high-accuracy foveal modules operating in parallel with lower-accuracy and faster modules that can operate across the visual field.

Central retinal vessel trunk exit location: An important factor while evaluating the neuroretinal rim.

Optic nerve head (ONH) evaluation plays a key role in differentiating normal from glaucomatous disk. Thinning of the inferior neuroretinal rim (NRR) has been noted in early glaucoma. However, NRR thickness in different quadrants appears to depend on various factors including central retinal vessel trunk exit (CRVT) position. We evaluated ocular parameters that determined the NRR thickness in the different quadrants of normal eyes. Retrospective review of demographic and ocular data from 773 eyes of 388 subjects with normal ONH over one year was undertaken. Nearly 54% were males, and the mean age was 43.2 years. The CRVT exit was central in 50% (773). The common site for noncentral CRVT was superotemporal (ST) [37%, 141/384] followed by inferotemporal (IT) [35%, 135/384]. With noncentral CRVT, the probability that the inferior, superior, nasal and temporal (ISNT) rule was not followed was 1.42 times ( P < 0.001). The thinnest rim quadrant (TRQ) was mostly ST (69%) irrespective of CRVT location. The TRQ was IT in 40% when CRVT was noncentral and 82% with IT CRVT exit. With noncentral CRVT, round disks favored noncompliance [132 (54.1%), odds ratio (OR) 2.56] with the ISNT rule. The OR of noncompliance with the ISNT rule increases 1.89 times with inferonasal CRVT and 1.22 times with a unit increase in the axial length. TRQ was IT in IT CRVT, and noncompliance with the ISNT rule was observed with large disks, longer axial length, and noncentral CRVT. This implies that despite the ISNT rule being violated these eyes do not have optic nerve pathology and should not be subjected to unnecessary diagnostic tests.

Spikiness and animacy as potential organizing principles of human ventral visual cortex.

Considerable research has been devoted to understanding the fundamental organizing principles of the ventral visual pathway. A recent study revealed a series of 3-4 topographical maps arranged along the macaque inferotemporal (IT) cortex. The maps articulated a two-dimensional space based on the spikiness and animacy of visual objects, with "inanimate-spiky" and "inanimate-stubby" regions of the maps constituting two previously unidentified cortical networks. The goal of our study was to determine whether a similar functional organization might exist in human IT. To address this question, we presented the same object stimuli and images from "classic" object categories (bodies, faces, houses) to humans while recording fMRI activity at 7 Tesla. Contrasts designed to reveal the spikiness-animacy object space evoked extensive significant activation across human IT. However, unlike the macaque, we did not observe a clear sequence of complete maps, and selectivity for the spikiness-animacy space was deeply and mutually entangled with category-selectivity. Instead, we observed multiple new stimulus preferences in category-selective regions, including functional sub-structure related to object spikiness in scene-selective cortex. Taken together, these findings highlight spikiness as a promising organizing principle of human IT and provide new insights into the role of category-selective regions in visual object processing.

Macaques recognize features in synthetic images derived from ventral stream neurons

Primates can recognize features in virtually all types of images, an ability that still requires a comprehensive computational explanation. One hypothesis is that visual cortex neurons learn patterns from scenes, objects, and textures, and use these patterns to interpolate incoming visual information. We have used machine learning algorithms to instantiate visual patterns stored by neurons-we call these highly activating images prototypes. Prototypes from inferotemporal (IT) neurons often resemble parts of real-world objects, such as monkey faces and body parts, a similarity established via pretrained neural networks [C. R. Ponce et al.,Cell 177, 999-1009.e10 (2019)]and naïve human participants [A. Bardon, W. Xiao, C. R. Ponce, M. S. Livingstone, G. Kreiman, Proc. Natl. Acad. Sci. U.S.A. 119, e2118705119 (2022)]. However, it is not known whether monkeys themselves perceive similarities between neuronal prototypes and real-world objects. Here, we investigated whether monkeys reported similarities between prototypes and real-world objects using a two-alternative forced choice task. We trained the animals to saccade to synthetic images of monkeys, and subsequently tested how they classified prototypes synthesized from IT and primary visual cortex (V1). We found monkeys classified IT prototypes as conspecifics more often than they did random generator images and V1 prototypes, and their choices were partially predicted by convolutional neural networks. Further, we confirmed that monkeys could abstract general shape information from images of real-world objects. Finally, we verified these results with human participants. Our results provide further evidence that prototypes from cortical neurons represent interpretable abstractions from the visual world.

Bidirectional and parallel relationships in macaque face circuit revealed by fMRI and causal pharmacological inactivation

Although the presence of face patches in primate inferotemporal (IT) cortex is well established, the functional and causal relationships among these patches remain elusive. In two monkeys, muscimol was infused sequentially into each patch or pair of patches to assess their respective influence on the remaining IT face network and the amygdala, as determined using fMRI. The results revealed that anterior face patches required input from middle face patches for their responses to both faces and objects, while the face selectivity in middle face patches arose, in part, from top-down input from anterior face patches. Moreover, we uncovered a parallel fundal-lateral functional organization in the IT face network, supporting dual routes (dorsal-ventral) in face processing within IT cortex as well as between IT cortex and the amygdala. Our findings of the causal relationship among the face patches demonstrate that the IT face circuit is organized into multiple functional compartments.

Racial Differences in Detection of Glaucoma Using Retinal Nerve Fiber Layer Thickness and Bruch Membrane Opening Minimum Rim Width

To compare the sensitivities and specificities of the retinal nerve fiber layer thickness (RNFLT) and Bruch membrane opening minimum rim width (BMO-MRW) reference database-based criteria for detection of glaucoma in individuals of European descent (ED) and individuals of African descent (AD). Comparative diagnostic analysis by race METHODS: 382 eyes of 255 glaucoma patients (ED=170, AD=85) and 94 eyes of 50 healthy individuals (ED=30, AD=20) with global and sectoral RNFLT and BMO-MRW measured with Spectralis optical coherence tomography (OCT) were included. Six diagnostic criteria were evaluated: global measurement below the 5th or 1st percentile, ≥1 of the 6 sector measurements below the 5th or 1st percentile, and superotemporal (ST) and/or inferotemporal (IT) measurement below the 5th or 1st percentile. The sensitivities and specificities of these measurements for detection of glaucoma were compared using bootstrapping methods. ST and/or IT RNFLT below the 5th percentile has the best performance for detection of glaucoma among RNFLT classifications with a sensitivity (95% CI) of 89.5% (86.1, 92.5) and specificity of 87.2% (77.8, 95.1). In AD individuals, sensitivities of ST and IT RNFLT and BMO-MRW measurements below the 5th percentile criteria were lower than in ED individuals (RNFLT: 83.7% vs 92.5%, and BMO-MRW: 72.1% vs 88.5%, respectively), as well as specificities (AD RNFLT: 73.7% and BMO-MRW: 89.5% vs ED RNFLT: 96.4% and BMO-MRW: 98.2%, respectively). RNFLT and BMO-MRW had consistently lower diagnostic performance in AD individuals compared with ED individuals. BMO-MRW criteria might fail to detect as many as one-third of eyes with glaucoma, specifically in AD individuals. With the current reference database, RNFLT, and especially BMO-MRW, criteria are not adequate for diagnosing glaucoma in AD individuals.

A connectivity-constrained computational account of topographic organization in primate high-level visual cortex

Inferotemporal (IT) cortex in humans and other primates is topographically organized, containing multiple hierarchically organized areas selective for particular domains, such as faces and scenes. This organization is commonly viewed in terms of evolved domain-specific visual mechanisms. Here, we develop an alternative, domain-general and developmental account of IT cortical organization. The account is instantiated in interactive topographic networks (ITNs), a class of computational models in which a hierarchy of model IT areas, subject to biologically plausible connectivity-based constraints, learns high-level visual representations optimized for multiple domains. We find that minimizing a wiring cost on spatially organized feedforward and lateral connections, alongside realistic constraints on the sign of neuronal connectivity within model IT, results in a hierarchical, topographic organization. This organization replicates a number of key properties of primate IT cortex, including the presence of domain-selective spatial clusters preferentially involved in the representation of faces, objects, and scenes; columnar responses across separate excitatory and inhibitory units; and generic spatial organization whereby the response correlation of pairs of units falls off with their distance. We thus argue that topographic domain selectivity is an emergent property of a visual system optimized to maximize behavioral performance under generic connectivity-based constraints.

The role of temporal cortex in the control of attention.

Attention is an indispensable component of active vision. Contrary to the widely accepted notion that temporal cortex processing primarily focusses on passive object recognition, a series of very recent studies emphasize the role of temporal cortex structures, specifically the superior temporal sulcus (STS) and inferotemporal (IT) cortex, in guiding attention and implementing cognitive programs relevant for behavioral tasks. The goal of this theoretical paper is to advance the hypothesis that the temporal cortex attention network (TAN) entails necessary components to actively participate in attentional control in a flexible task-dependent manner. First, we will briefly discuss the general architecture of the temporal cortex with a focus on the STS and IT cortex of monkeys and their modulation with attention. Then we will review evidence from behavioral and neurophysiological studies that support their guidance of attention in the presence of cognitive control signals. Next, we propose a mechanistic framework for executive control of attention in the temporal cortex. Finally, we summarize the role of temporal cortex in implementing cognitive programs and discuss how they contribute to the dynamic nature of visual attention to ensure flexible behavior.

Unsupervised deep learning identifies semantic disentanglement in single inferotemporal face patch neurons

In order to better understand how the brain perceives faces, it is important to know what objective drives learning in the ventral visual stream. To answer this question, we model neural responses to faces in the macaque inferotemporal (IT) cortex with a deep self-supervised generative model, β-VAE, which disentangles sensory data into interpretable latent factors, such as gender or age. Our results demonstrate a strong correspondence between the generative factors discovered by β-VAE and those coded by single IT neurons, beyond that found for the baselines, including the handcrafted state-of-the-art model of face perception, the Active Appearance Model, and deep classifiers. Moreover, β-VAE is able to reconstruct novel face images using signals from just a handful of cells. Together our results imply that optimising the disentangling objective leads to representations that closely resemble those in the IT at the single unit level. This points at disentangling as a plausible learning objective for the visual brain.

Agreement Between Trend-Based and Qualitative Analysis of the Retinal Nerve Fiber Layer Thickness for Glaucoma Progression on Spectral-Domain Optical Coherence Tomography.

IntroductionTo evaluate the agreement between trend-based analysis and qualitative assessment of the retinal nerve fiber layer (RNFL) thickness for glaucomatous progression on spectral-domain optical coherence tomography (SDOCT).MethodsRetrospective review of 190 eyes from 103 patients with glaucoma or suspected glaucoma that underwent SDOCT imaging during four consecutive clinic visits. Trend-based progression was characterized by a significantly negative slope. Progression by qualitative analysis was determined by review of raw SDOCT B-scans.ResultsThe slope was significantly greater in those with progression than without progression for both trend-based and qualitative analysis (p < 0.001). However, the qualitative grading classified a significantly greater proportion of eyes as progressing compared to trend-based analysis in both the superotemporal (ST) (23.2% vs. 10.5%, p = 0.001) and inferotemporal (IT) RNFL (27.4% vs 8.4%, p < 0.001). The trend-based and qualitative classifications of progression showed poor agreement in both the ST (kappa = 0.0135) and IT RNFL (kappa = 0.1222). The agreement between trend-based and qualitative analysis was lower for eyes with artifacts (ST = 58.11%; IT = 68.7%) than those without artifacts (ST = 80.2%; IT = 74.8%). Moreover, among eyes with artifacts, there was no significant difference in slope between those qualitatively categorized as progressing versus not progressing (p > 0.05).ConclusionsPoor agreement was found between a trend-based and qualitative analysis of change in RNFL on SDOCT. Careful qualitative review of SDOCT imaging may identify specific areas of glaucoma progression not captured by trend-based methods, especially in the presence of artifacts. Such an approach may also prove useful for detecting glaucoma progression in a clinical setting when there are few data points available.

Explaining face representation in the primate brain using different computational models

Understanding how the brain represents the identity of complex objects is a central challenge of visual neuroscience. The principles governing object processing have been extensively studied in the macaque face patch system, a sub-network of inferotemporal (IT) cortex specialized for face processing. A previous study reported that single face patch neurons encode axes of a generative model called the "active appearance" model, which transforms 50D feature vectors separately representing facial shape and facial texture into facial images. However, a systematic investigation comparing this model to other computational models, especially convolutional neural network models that have shown success in explaining neural responses in the ventral visual stream, has been lacking. Here, we recorded responses of cells in the most anterior face patch anterior medial (AM) to a large set of real face images and compared a large number of models for explaining neural responses. We found that the active appearance model better explained responses than any other model except CORnet-Z, a feedforward deep neural network trained on general object classification to classify non-face images, whose performance it tied on some face image sets and exceeded on others. Surprisingly, deep neural networks trained specifically on facial identification did not explain neural responses well. A major reason is that units in the network, unlike neurons, are less modulated by face-related factors unrelated to facial identification, such as illumination.

Pinpointing the neural signatures of single-exposure visual recognition memory

Memories of the images that we have seen are thought to be reflected in the reduction of neural responses in high-level visual areas such as inferotemporal (IT) cortex, a phenomenon known as repetition suppression (RS). We challenged this hypothesis with a task that required rhesus monkeys to report whether images were novel or repeated while ignoring variations in contrast, a stimulus attribute that is also known to modulate the overall IT response. The monkeys' behavior was largely contrast invariant, contrary to the predictions of an RS-inspired decoder, which could not distinguish responses to images that are repeated from those that are of lower contrast. However, the monkeys' behavioral patterns were well predicted by a linearly decodable variant in which the total spike count was corrected for contrast modulation. These results suggest that the IT neural activity pattern that best aligns with single-exposure visual recognition memory behavior is not RS but rather sensory referenced suppression: reductions in IT population response magnitude, corrected for sensory modulation.

Frontotemporal coordination predicts working memory performance and its local neural signatures

Neurons in some sensory areas reflect the content of working memory (WM) in their spiking activity. However, this spiking activity is seldom related to behavioral performance. We studied the responses of inferotemporal (IT) neurons, which exhibit object-selective activity, along with Frontal Eye Field (FEF) neurons, which exhibit spatially selective activity, during the delay period of an object WM task. Unlike the spiking activity and local field potentials (LFPs) within these areas, which were poor predictors of behavioral performance, the phase-locking of IT spikes and LFPs with the beta band of FEF LFPs robustly predicted successful WM maintenance. In addition, IT neurons exhibited greater object-selective persistent activity when their spikes were locked to the phase of FEF LFPs. These results reveal that the coordination between prefrontal and temporal cortex predicts the successful maintenance of visual information during WM.