Biology subjects

Reznik, D.

Publications and source records attributed to Reznik, D..

8 recordsLinked to original sources

bioRxiv2026

Distinct cortical networks associated with subregions of the hippocampal-entorhinal system in the first two years of human life

Episodic memory critically depends on the hippocampus and the entorhinal cortex. Despite a rapid developmental change in human episodic memory during the first two years of life, little is known about the developmental trajectory of the hippocampal-entorhinal circuitry during this critical time period. In the current study, we collected high-quality precision fMRI data from five typically developing infants over the time period between 1 and 2 years of life and examined, in great anatomical detail, the developmental profile of distinct parts of the infant hippocampal-entorhinal system and their coupling with distinct cortical networks. We show that already at around 1 year of age, subdivisions of the canonical default network (DN) are fully dissociated at the neocortex and are differently associated with the hippocampal-entorhinal system, with tentatively differential developmental trajectories. While the DN-A, associated with episodic simulation, coupled with the anterior hippocampus and the medial part of the entorhinal cortex, the DN-B, associated with social cognition, showed significantly weaker connectivity with the hippocampal-entorhinal system. Furthermore, the parietal memory network coupled with the posterior hippocampus and the lateral part of the entorhinal cortex. Exploratory longitudinal results suggest that associations of the DN-B with the hippocampus and the entorhinal cortex increase towards the end of the second postnatal year, and the associations of the parietal memory network become more topographically restricted to the posterior hippocampus. These networks and their differential maturation may provide the basis for important developments in episodic memory and social cognition in the second postnatal year and suggest that potentially unique properties of human hippocampal-entorhinal circuitry may emerge latest in development.

neuroscience↗

bioRxiv2024

Hippocampal-entorhinal cognitive maps and cortical motor system represent action plans and their outcomes

Efficiently interacting with the environment requires weighing and selecting among multiple alternative actions based on their associated outcomes. However, the neural mechanisms underlying these processes are still debated. We showed that forming relations between arbitrary action-outcome associations involved building a cognitive map. Using a novel immersive virtual reality paradigm, participants learned 2D abstract motor action-outcome associations and later compared action combinations while their brain activity was monitored with fMRI. We observed a hexadirectional modulation of the activity in entorhinal cortex while participants compared different action plans. Furthermore, hippocampal activity scaled with the 2D similarity between outcomes of these action plans. Conversely, the supplementary motor area (SMA) represented individual actions, showing a stronger response to overlapping action plans. Crucially, the connectivity between hippocampus and SMA was modulated by the similarity between the action plans, suggesting their complementary roles in action evaluation. These findings provide evidence for the role of cognitive maps in action selection, challenging classical models of memory taxonomy and its neural bases.

neuroscience↗

bioRxiv2024

Phylogeny of neocortical-hippocampal projections provides insight in the nature of human memory

The study of cross-species differences in the organization of the cerebral cortex received significant attention during the past century. However, the evolutionary principles governing changes in brain connectivity and their impact on cognition remain poorly understood. In the current study, we analysed differences in anatomical input from the cerebral cortex to the hippocampal region across six species spanning more than 100 million years of mammalian evolution - the tenrec, rat, cat, marmoset, macaque, and human. Our results demonstrate that unlike direct transmodal cortical input, direct unimodal cortical input to the hippocampal region was selectively eliminated with the increase in brain size. Additionally, input from primary sensory regions was eliminated prior to input from non-primary sensory regions. Our findings suggest that hippocampus-related processes in different species operate on fundamentally different types of information, potentially underpinning cross-species differences in hippocampus-dependent cognition. Furthermore, our findings outline the evolutionary trajectory of the anatomical circuitry associating the human hippocampal region with the neocortex.

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bioRxiv2024

High or Low Expectations: Expected intensity of action outcome is embedded in action ‎kinetics

Goal-directed actions are performed in order to attain certain sensory consequences in the world. However, expected attributes of these consequences can affect the kinetics of the action. In a set of three studies (n=120), we examined how expected attributes of stimulus outcome (intensity) shape the kinetics of the triggering action (applied force), even when the action and attribute are independent. We show that during action execution (button presses), the expected intensity of sensory outcome implicitly affects the applied force of the stimulus-producing action in an inverse fashion. Thus, participants applied more force when the expected intensity of the outcome was low (vs. high intensity outcome). In the absence of expectations or when actions were performed in response to the sensory event, no intensity-dependent force modulations were found. Thus, causality and expectations of stimulus intensity play an important role in shaping action kinetics. Finally, we examined the relationship between kinetics and perception and found no influence of applied force level on perceptual detection of low intensity (near-threshold) outcome stimuli, suggesting no causal link between the two. Taken together, our results demonstrate that action kinetics are implicitly embedded with high-level context such as the expectation of consequence intensity and the causal relationship with environmental cues.

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bioRxiv2022

A combined DTI-fMRI approach for optimizing the delineation of posteromedial vs. anterolateral entorhinal cortex

In the entorhinal cortex (EC), attempts have been made to identify the human homologue regions of the medial (MEC) and lateral (LEC) subdivision using either functional magnetic resonance imaging (fMRI) or diffusion tensor imaging (DTI). However, there are still discrepancies between entorhinal subdivisions depending on the choice of connectivity seed regions and the imaging modality used. While DTI can be used to follow the white matter tracts of the brain, fMRI can identify functionally connected brain regions. In this study, we used both DTI and resting-state fMRI in 103 healthy adults to investigate both structural and functional connectivity between the EC and associated cortical brain regions. Differential connectivity with these regions was then used to predict the locations of the human homologues of MEC and LEC. Our results from combining DTI and fMRI support a subdivision into posteromedial (pmEC) and anterolateral (alEC) EC and reveal a confined border between the pmEC and alEC. Furthermore, the EC subregions obtained by either imaging modality showed similar distinct connectivity patterns: While pmEC showed increased connectivity preferentially with the default mode network, the alEC exhibited increased connectivity with regions in the dorsal attention and salience networks. Optimizing the delineation of the human homologues of MEC and LEC with a combined, cross-validated DTI-fMRI approach allows to define a likely border between the two subdivisions and has implications for both cognitive and translational neuroscience research.

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bioRxiv2020

Motor-evoked neural responses in auditory cortex are associated with improved sensitivity to self-generated sounds

Sensory perception is a product of complex interactions between the internal state of an organism and the physical attributes of a stimulus. One factor that modulates the internal state of the perceiving agent is voluntary movement. It has been shown across the animal kingdom that perception and sensory-evoked physiological responses are modulated depending on whether or not the stimulus is the consequence of voluntary actions. These phenomena are often attributed to motor signals sent to relevant sensory regions (efference copies), that convey information about expected upcoming sensory consequences. However, to date, there is no direct evidence in humans for efferent signals underlying these motor-sensory interactions. In the current study we recorded neurophysiological (using Magnetoencephalography) and behavioral responses from 16 healthy subjects performing an auditory detection task of faint tones. Tones were either generated by subjects voluntary button presses or occurred predictably following a visual cue. By introducing a constant temporal delay between button press/cue and tone delivery and applying source-level analysis we decoupled motor-evoked and auditory-evoked activity in auditory cortex. We show motor-related evoked-responses in auditory cortex following sound-triggering actions and preceding sound onset. Such evoked-responses were not found for button-presses that were not coupled with expected sounds. Furthermore, the amplitude of these evoked-responses corresponded with subsequent sound detection, suggesting their functional relevance to auditory processing. Our results provide first direct evidence for efferent signals in sensory cortex that are evoked by voluntary actions coupled with sensory consequences.

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bioRxiv2020

Voluntary actions modulate perception and neural representation of action-consequences in a hand-dependent manner

Evoked neural activity in sensory regions, and perception of sensory stimuli, are modulated when the stimuli are the consequence of voluntary movement as opposed to an external source. It has been suggested that such modulations are due to efference copies of the motor command that are sent to relevant sensory regions during voluntary movement. Given the anatomical-functional laterality bias of the motor system, it is plausible that the pattern of such behavioral and neural sensory modulations will exhibit a similar bias, depending on the effector that was used to trigger the stimulus (e.g. right / left hand). Here we examined this issue in the visual domain using behavioral and neural measures (fMRI). Healthy participants judged the relative brightness of identical visual stimuli that were either self-triggered (using right or left hand button presses), or triggered by the computer. By presenting stimuli to either the right or left visual field, we biased visual-evoked responses to left / right visual cortex. We found stronger perceptual modulations when the triggering hand was ipsi (rather than contra) lateral to the stimulated visual field. At the neural level, we found that despite identical physical properties of the visual consequence, evoked fMRI responses in right and left visual cortices differentiate the identity of the triggering hand (left / right). Our findings support a model in which voluntary actions induce sensory modulations that follow the anatomical-functional bias of the motor system.

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bioRxiv2017

Predicted sensory consequences of voluntary actions modulate amplitude and temporal dynamics of preceding readiness potentials

Self-generated, voluntary actions, are preceded by a slow negativity in the scalp electroencephalography (EEG) signal recorded from frontal regions (termed readiness potential; RP). This signal, and its lateralized subcomponent (LRP), is mainly regarded as preparatory motor activity associated with the forthcoming motor act. However, it is not clear whether this neural signature is associated with preparatory motor activity, expectation of its associated sensory consequences, or both. Here we recorded EEG data from 12 healthy subjects while they performed self-paced button presses with their right index and middle fingers. In one condition (motor+sound) these button-presses triggered a sound while in another (motor-only) they did not. Additionally, subjects passively listened to sounds delivered in expected timings (sound-only). We found that the RP amplitude (locked to time of button press) was significantly more negative in the motor+sound compared with motor-only conditions starting ~1.4 seconds prior to button press. Importantly, no signal negativity was observed prior to expected sound delivery in the sound-only condition. Thus, the differences in RP amplitude between motor+sound and motor-only conditions are beyond differences in mere expectation of a forthcoming auditory sound. No significant differences between the two conditions were obtained in the LRP component. Our results suggest that expected auditory consequences are encoded in the early phase of the RP preceding the voluntary actions that generate them.

neuroscience↗