Biology subjects

Armendariz, M.

Publications and source records attributed to Armendariz, M..

4 recordsLinked to original sources

bioRxiv2025

Single-neuron encoding of rapidly learned visual information reshapes human perception

Humans can swiftly learn to recognize visual objects after minimal exposure. Integrating new information with existing knowledge requires forming enduring neuronal representations to enable future recognition. Yet, the neuronal mechanisms in the human brain underlying such rapid perceptual changes remain unclear. We recorded single-neuron activity in occipital (OC) and medial temporal lobe (MTL) regions as participants rapidly learned to recognize degraded images. OC and MTL neurons modulated their activity to encode newly learned visual information and reshape perception. Population decoding revealed that OC neurons required additional processing time to resolve the identity of learned images, delaying neuronal responses in the MTL. Our findings indicate that OC supports recognition after rapid learning via extensive recurrent processing, potentially involving higher-order neocortical areas, without relying on feedback from MTL. These results provide mechanistic constraints for biologically plausible models of visual recognition and few-shot visual learning.

neuroscience↗

bioRxiv2023

An adversarial collaboration to critically evaluate theories of consciousness

Different theories explain how subjective experience arises from brain activity1,2. These theories have independently accrued evidence, yet, confirmation bias and dependence on design choices hamper progress in the field3. Here, we present an open science adversarial collaboration which directly juxtaposes Integrated Information Theory (IIT)4,5 and Global Neuronal Workspace Theory (GNWT)6-10, employing a theory-neutral consortium approach11,12. We investigate neural correlates of the content and duration of visual experience. The theory proponents and the consortium developed and preregistered the experimental design, divergent predictions, expected outcomes, and their interpretation12. 256 human subjects viewed suprathreshold stimuli for variable durations while neural activity was measured with functional magnetic resonance imaging, magnetoencephalography, and electrocorticography. We find information about conscious content in visual, ventro-temporal and inferior frontal cortex, with sustained responses in occipital and lateral temporal cortex reflecting stimulus duration, and content-specific synchronization between frontal and early visual areas. These results confirm some predictions of IIT and GNWT, while substantially challenging both theories: for IIT, a lack of sustained synchronization within posterior cortex contradicts the claim that network connectivity specifies consciousness. GNWT is challenged by the general lack of ignition at stimulus offset and limited representation of certain conscious dimensions in prefrontal cortex. Beyond challenging the theories themselves, we present an alternative approach to advance cognitive neuroscience through a principled, theory-driven, collaborative effort. We highlight the challenges to change peoples mind 13 and the need for a quantitative framework integrating evidence for systematic theory testing and building.

neuroscience↗

bioRxiv2018

The autism and schizophrenia-associated protein CYFIP1 regulates bilateral brain connectivity

Copy-number variants of the CYFIP1 gene in humans have been linked to Autism and Schizophrenia, two neuropsychiatric disorders characterized by defects in brain connectivity. CYFIP1 regulates molecular events underlying post-synaptic functions. Here, we show that CYFIP1 plays an important role in brain functional connectivity and callosal functions. In particular, we find that Cyfip1 heterozygous mice have reduced brain functional connectivity and defects in white matter architecture, typically relating to phenotypes found in patients with Autism, Schizophrenia and other neuropsychiatric disorders. In addition, Cyfip1 deficient mice present deficits in the callosal axons, namely reduced myelination, altered pre-synaptic function, and impaired bilateral-connectivity related behavior. Altogether, our results show that Cyfip1 haploinsufficiency compromises brain connectivity and function, which might explain its genetic association to neuropsychiatric disorders.

neuroscience↗

bioRxiv2018

Neural basis of Transcranial Magnetic Stimulation at the single-cell Level

Transcranial Magnetic Stimulation (TMS) can non-invasively modulate neural activity in humans. Despite three decades of research, the spatial extent of the cortical area activated by TMS is still controversial. Moreover, how TMS interacts with task-related activity during motor behavior is unknown. We applied single-pulse TMS over the macaque parietal cortex while recording single-unit activity at various distances from the center of stimulation during grasping. The spatial extent of the TMS-induced activation was remarkably restricted, affecting single neurons in a volume of cortex measuring less than 2 mm. In task-related neurons, TMS evoked a transient excitation followed by reduced activity, which was paralleled by a significantly longer grasping time. Furthermore, TMS- induced activity and task-related activity did not summate in single neurons. These results furnish crucial experimental evidence for the neural basis of the TMS effect at the single-cell level and uncover, the neural underpinnings of behavioral effects of TMS.

neuroscience↗