Biology subjects

Diamond, M. E.

Publications and source records attributed to Diamond, M. E..

11 recordsLinked to original sources

bioRxiv2026

Behavioral signatures suggest distinct modes of suppressing irrelevant information during tactile temporal attention in human participants

To make adaptive perceptual judgments, the nervous system must selectively process behaviorally relevant sensory information while filtering out competing distractions. Although attentional control has been extensively studied in the visual domain, particularly in the context of spatial selection, considerably less is known about how attention operates in the tactile modality and across time rather than space. Here, we developed a paradigm to investigate temporal tactile attention in human participants, enabling the study of attentional behavior and underlying behavioral strategies in this sensory domain. Participants were instructed to categorize the intensity of a task-relevant tactile stimulus delivered to the fingertip while ignoring an irrelevant tactile stimulus. A visual cue indicated which of two sequentially presented stimuli was relevant on each trial. In addition, participants completed self-report questionnaires assessing autistic traits and aberrant salience (the tendency to assign significance to otherwise neutral stimuli or events). Across subjects, participants performed the task with high accuracy. However, clustering analyses based on behavioral features revealed distinct response profiles. One cluster did not exhibit biases induced by the irrelevant stimulus. In contrast, a third cluster displayed a repulsive effect of the irrelevant stimulus and showed lower overall performance. These behavioral phenotypes were also reflected, to some extent, in differences in learning trajectories across training sessions. We further explored participants' metacognitive awareness through a post-experiment questionnaire assessing subjective evaluations of task difficulty and performance. Although exploratory, the results suggest a relationship between metacognitive reports, behavioral strategies, and objective task performance. In contrast, neither autistic traits nor aberrant salience scores were associated with performance measures or behavioral phenotypes. Together, these findings support the view that attentional control is implemented through multiple, individualistic behavioral strategies rather than a single mechanism pertaining to all, suggesting that task structure interacts with individual predispositions to shape distinct modes of attentional control in human participants.

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bioRxiv2026

Individual strategies for ignoring irrelevant information are reflected in distinct neural signatures during temporal attention.

Attentional functions enable the nervous system to regulate incoming information, selecting what is behaviorally relevant while filtering out distractions. To investigate attentional control in rats, we developed a paradigm in which animals are required to ignore an irrelevant tactile stimulus (a vibration) and categorize the relevant one as weak or strong. Stimuli were separated in time but delivered to the same set of vibrissae, making this a temporal rather than spatial attention task. In the first task version, the irrelevant stimulus was presented first and the relevant second. Across animals, we observed substantial variability in how this task was learned and performed, consistent with emerging work showing that learning unfolds along idiosyncratic trajectories rather than converging on a single behavioral solution. While the irrelevant stimulus typically exerted an attractive bias on judgments, some rats progressively reduced this influence and achieved near-complete suppression, transitioning from a proficient to an expert stage of performance. Other animals, however, adopted alternative stable strategies and did not exhibit comparable levels of attentional filtering. To probe behavioral flexibility, we designed a version of the task in which the relevant stimulus could appear in either temporal position. Under these conditions, rats generally struggled to flexibly allocate attention across time, again with substantial variability across individuals. Importantly, behavioral analyses indicate that this variability is not random but reflects a small number of reproducible strategy classes, characterized by distinct patterns of sensitivity to stimulus order. These findings suggest that attentional control in this task does not rely on a single canonical algorithm, but instead emerges from a constrained set of alternative solutions. Electrophysiological recordings from a limited number of animals revealed neural correlates consistent with these behavioral differences. In expert animals performing the original task, neuronal populations in motor cortex showed differential encoding of the irrelevant and relevant stimuli. In a proficient animal implanted in both vS1 and M1/M2, outcome-dependent modulation was prominent in vS1, whereas M1/M2 transformed sensory inputs into categorical representations with partial suppression of the irrelevant stimulus. Local field potential analyses further indicated that effective task performance was associated with increased high gamma synchronization between vS1 and M1/M2, alongside low-beta modulation consistent with top-down interactions. Taken together, these results suggest that learning to ignore irrelevant information reshapes interactions between sensory and motor cortices, but that this process unfolds heterogeneously across individuals. Rather than reflecting a single mechanism of attentional control, the data support a framework in which multiple, identifiable strategies coexist within a shared task structure, underscoring the importance of individual differences in understanding the neural basis of attention.

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bioRxiv2026

Independent history traces for distinct percepts derived from a single stimulus

Perception is more than a direct readout of current sensory input; it is also shaped by recent experience, a phenomenon known as serial dependence. While the effects of recent experience have been well characterized for single stimulus features, it remains unclear how perceptual history operates when multiple perceptual dimensions must be extracted from a single sensory event. Here, human participants reported their judgment of vibrotactile stimuli, with the relevant feature - either the intensity or duration - randomly cued on each trial. Within trials, intensity and duration interacted bidirectionally - longer stimuli were perceived as stronger and stronger stimuli as longer - indicating that both features are derived from a shared sensory representation. Across trials, however, serial dependence was feature-specific: perceived intensity was selectively attracted toward previously perceived intensities, and perceived duration toward previously perceived durations. The current trial judgment was influenced by perceptual estimates from multiple preceding trials, but only those in which the same feature was task-relevant. We formalize these findings with a computational model in which perceptual history is maintained in parallel memory traces, each selectively updated when the corresponding feature is task-relevant. The model captured both the psychometric structure of behavior and the feature-specific, multi-trial dependence of perceptual judgments, with traces that accumulate past percepts and bias current estimates along the corresponding feature dimension.Serial dependence in this task operates on perceptual representations downstream of a shared sensory encoding stage, and is maintained simultaneously in feature-specific, task-gated memory traces within higher-level cortical circuits.

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bioRxiv2026

Cortical population codes for embedding sensory inputs into the prior context

According to theories of the brain as a predictive network, perceptual decisions result from integrating incoming sensory inputs with prior experience. A neuronal population implementing this form of computation must not only retain information about past events, but also combine this information with current sensory evidence. To examine how this integration occurs, we recorded extracellular activity from both primary sensory cortex and a target frontal region in rats performing stimulus categorization. Psychophysical analysis showed that judgments were history-dependent. Sensory cortex represented the current stimulus largely independently of prior stimuli and failed to account for the history-dependence seen in behavior. By contrast, frontal cortex embedded current input within a representation of prior sensory information through collinearity in coding dimensions. This mechanism - predominantly mediated by fast-spiking neurons - explained trial-to-trial variability in decisions. Our findings argue for distinct roles of cortical regions in predictive processing, and identify a frontal stage where current and prior sensory information converge to inform decisions.

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bioRxiv2024

Diverse perceptual biases emerge from Hebbian plasticity in a recurrent neural network model

Perceptual biases offer a glimpse into how the brain processes sensory stimuli. While psycho-physics has uncovered systematic biases such as contraction (stored information shifts towards a central tendency), and repulsion (the current percept shifts away from recent percepts), a unifying neural network model for how such seemingly distinct biases emerge from learning is lacking. Here, we show that both contractive and repulsive biases emerge from continuous Hebbian plasticity in a single recurrent neural network. We test the model in four different datasets, two sensory modalities and three experimental paradigms: two working memory tasks, a reference memory task, and a novel "one-back task" that we designed to test the robustness of the model. We find excellent agreement between model predictions and experimental data without fine-tuning the model to any particular paradigm. These results show that apparently contradictory perceptual biases can in fact emerge from a simple local learning rule in a single recurrent region of the brain.

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bioRxiv2021

The sensory code within sense of time

Sensory experiences are accompanied by the perception of the passage of time; a cell phone vibration, for instance, is sensed as brief or long. The neuronal mechanisms underlying the perception of elapsed time remain unknown1. Recent work agrees on a role for cortical processing networks2,3, however the causal function of sensory cortex in time perception has not yet been specified. We hypothesize that the mechanisms for time perception are embedded within primary sensory cortex and are thus governed by the basic rules of sensory coding. By recording and optogenetically modulating neuronal activity in rat vibrissal somatosensory cortex, we find that the percept of stimulus duration is dilated and compressed by optogenetic excitation and inhibition, respectively, during stimulus delivery. A second set of rats judged the intensity of tactile stimuli; here, optogenetic excitation amplified the intensity percept, demonstrating sensory cortex to be the common gateway to both time and stimulus feature processing. The coding algorithms for sensory features are well established4-10. Guided by these algorithms, we formulated a 3-stage model beginning with the membrane currents evoked by vibrissal and optogenetic drive and culminating in the representation of perceived time; this model successfully replicated rats choices. Our finding that stimulus coding is intrinsic to sense of time disagrees with dedicated pacemaker-accumulator operation models11-13, where sensory input acts only to trigger the onset and offset of the timekeeping process. Time perception is thus as deeply intermeshed within the sensory processing pathway as is the sense of touch itself14,15 and can now be treated through the computational language of sensory coding. The model presented here readily generalizes to humans14,16 and opens up new approaches to understanding the time misperception at the core of numerous neurological conditions17,18.

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bioRxiv2020

Conserved visual capacity of rats under red light

Recent studies examine the behavioral capacities of rats and mice with and without visual input, and the neuronal mechanisms underlying such capacities. These animals are assumed to be functionally blind under red light, an assumption that might originate in the fact that they are dichromats who possess ultraviolet and green but not red cones. But the inability to see red as a color does not necessarily rule out form vision based on red light absorption. We measured Long-Evans rats capacity for visual form discrimination under red light of various wavelength bands. Upon viewing a black and white grating, they had to distinguish between two categories of orientation, horizontal and vertical. Psychometric curves plotting judged orientation versus angle demonstrate the conserved visual capacity of rats under red light. Investigations aiming to explore rodent physiological and behavioral functions in the absence of visual input should not assume red-light blindness.

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bioRxiv2020

State-dependent changes in perception and coding in the mouse somatosensory cortex

An animals behavioral state is reflected in the dynamics of cortical population activity and its capacity to process sensory information. To better understand the relationship between behavioral states and information processing, mice are trained to detect varying amplitudes of whisker-deflection under two-photon calcium imaging. Layer 2/3 neurons (n=1436) in the vibrissal primary somatosensory cortex are imaged across different behavioral states, defined based on detection performance (low to high-state) and pupil diameter. The neurometric curve in each behavioral state mirrors the corresponding psychometric performance, with calcium signals predictive of the animals choice outcome. High behavioral states are associated with lower network synchrony, extending over shorter cortical distances. The decrease of correlations in variability across neurons in the high state results in enhanced information transmission capacity at the population level. The observed state-dependent changes suggest that the coding regime within the first stage of cortical processing may underlie adaptive routing of relevant information through the sensorimotor system. HighlightsO_LINetwork synchrony and pupil diameter are coupled to changes in behavioral state. C_LIO_LIHigh behavioral state results in enhanced information transmission capacity at the population level, with neurometric curve in each behavioral state mirroring the corresponding psychometric performance C_LIO_LIBehavioral state and calcium signal in primary somatosensory cortex predict choice outcome. C_LI eTOCO_ST_ABSIn BriefC_ST_ABSLee et al. investigates the relationship between behavioral states and information processing in the primary somatosensory cortex. They demonstrate increases in behavioral state results in decrease cortical variability, enhanced information transmission capacity and stimulus encoding at the population level.

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bioRxiv2020

A sensory integration account for time perception

The connection between stimulus perception and time perception remains unknown. The present study combines human and rat psychophysics with sensory cortical neuronal firing to construct a computational model for the percept of elapsed time embedded within sense of touch. When subjects judged the duration of a vibration applied to the fingertip (human) or whiskers (rat), increasing stimulus mean speed led to increasing perceived duration. Symmetrically, increasing vibration duration led to increasing perceived intensity. We modeled spike trains from vibrissal somatosensory cortex as input to dual leaky integrators - an intensity integrator with short time constant and a duration integrator with long time constant - generating neurometric functions that replicated the actual psychophysical functions of rats. Returning to human psychophysics, we then confirmed specific predictions of the dual leaky integrator model. This study offers a framework, based on sensory coding and subsequent accumulation of sensory drive, to account for how a feeling of the passage of time accompanies the tactile sensory experience.

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bioRxiv2019

Experience-related alterations in white matter structure and gene expression in adult rats

White matter (WM) plasticity during adulthood is a recently described phenomenon by which experience can shape brain structure. It has been observed in humans using diffusion tensor imaging (DTI). However, it remains unclear which mechanisms drive or underlie WM plasticity in adulthood. Here, we combined DTI and mRNA expression analysis and examined the effects of somatosensory experience in adult rats. Somatosensory experience resulted in differences in WM and grey matter structure. C-FOS mRNA expression, a marker of cortical activity, in the barrel cortex correlated with the structural WM measures, suggesting that WM plasticity is activity-dependent. Analysis of myelin-related genes revealed higher myelin basic protein expression in WM, while genome-wide RNA sequencing analysis identified 134 differentially-expressed genes regulating proteins involved in functions related to cell proliferation and differentiation, neuronal activity modulation and regulation of myelination. In conclusion, the macroscale measures of WM differences identified in response to somatosensory experience are supported by molecular evidence, which strongly suggest myelination as, at least, one of the underlying mechanisms.

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bioRxiv2017

Posterior parietal cortex represents sensory stimulus history and is necessary for its effects on behavior

Many models of cognition and of neural computations posit the use and estimation of prior stimulus statistics1-4: it has long been known that working memory and perception are strongly impacted by previous sensory experience, even when that sensory history is irrelevant for the current task at hand. Nevertheless, the neural mechanisms and brain regions necessary for computing and using such priors are unknown. Here we report that the posterior parietal cortex (PPC) is a critical locus for the representation and use of prior stimulus information. We trained rats in an auditory Parametric Working Memory (PWM) task, and found that rats displayed substantial and readily quantifiable behavioral effects of sensory stimulus history, similar to those observed in humans5,6 and monkeys7. Earlier proposals that PPC supports working memory8,9 predict that optogenetic silencing of this region would impair behavior in our working memory task. Contrary to this prediction, silencing PPC significantly improved performance. Quantitative analyses of behavior revealed that this improvement was due to the selective reduction of the effects of prior sensory stimuli. Electrophysiological recordings showed that PPC neurons carried far more information about sensory stimuli of previous trials than about stimuli of the current trial. Furthermore, the more information about previous trial sensory history in the neural firing rates of a given rats PPC, the greater the behavioral effect of sensory history in that rat, suggesting a tight link between behavior and PPC representations of stimulus history. Our results indicate that the PPC is a central component in the processing of sensory stimulus history, and open a window for neurobiological investigation of long-standing questions regarding how perception and working memory are affected by prior sensory information.

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