Time in a bottle. A psychophysics study of human time perception through aging Time perception is crucial for a coherent human experience. As life progresses, our perception of the passage of time becomes increasingly non-uniform, often feeling as though it accelerates with age. While various causes for this phenomenon have been theorized, a comprehensive mathematical and theoretical framework remains underexplored. This study aims to elucidate the mechanisms behind perceived time dilation by integrating classical and revised psychophysical theorems with a novel mathematical approach. Utilizing Weber-Fechner laws as foundational elements, we develop a model that transitions from exponential to logarithmic functions to represent changes in time perception across the human lifespan. Our results indicate that the perception of time shifts significantly around the age of mental maturity, aligning with a proposed inversion point where sensitivity to temporal stimuli decreases, eventually plateauing out at a constant rate. This model not only explains the underlying causes of time perception changes but also provides analytical values to quantify this acceleration. These findings offer valuable insights into the cognitive and neurological processes influencing how we experience time as we go through life.
Specific inhibition and disinhibition in the higher-order structure of a cortical connectome Neurons are thought to act as parts of assemblies with strong internal excitatory connectivity. Conversely, inhibition is often reduced to blanket inhibition with no targeting specificity. We analyzed the structure of excitation and inhibition in the MICrONS mm3 dataset, an electron microscopic reconstruction of a piece of cortical tissue. We found that excitation was structured around a feed-forward flow in large non-random neuron motifs with a structure of information flow from a small number of sources to a larger number of potential targets. Inhibitory neurons connected with neurons in specific sequential positions of these motifs, implementing targeted and symmetrical competition between them. None of these trends are detectable in only pairwise connectivity, demonstrating that inhibition is structured by these large motifs. While descriptions of inhibition in cortical circuits range from non-specific blanket-inhibition to targeted, our results describe a form of targeting specificity existing in the higher-order structure of the connectome. These findings have important implications for the role of inhibition in learning and synaptic plasticity.
Post-error slowing during motor sequence learning under extrinsic and intrinsic error feedback conditions Post-error slowing, described as an error-corrective index of response binding during motor sequence learning, has only been demonstrated in the serial reaction time task under conditions where extrinsic error feedback is presented. The present experiment investigated whether post-error slowing is dependent on, or is influenced by, extrinsic error feedback. Thirty participants (14 females, Mage = 21.9 1.8 years) completed the serial reaction time task with or without presentation of extrinsic error feedback. Post-error slowing was observed following response error whether feedback was presented or not. However, presentation of extrinsic error feedback increased post-error slowing across practice and extended the number of responses that were slowed following an error. There was no evidence of feedback effects on motor sequence learning or explicit awareness. Instead, feedback appeared to function as a performance factor that reduced response error rates relative to no feedback conditions. These findings illustrate that post-error slowing in motor sequence learning is not reliant on or a result of presentation of extrinsic error information. More specific to the serial reaction time task paradigm, the present findings demonstrate that the common practice of presenting error feedback is not necessary for investigating motor sequence learning unless the aim is to maintain low error rate. However, doing so might inflate reaction time in latter training blocks.
Sequence action representations contextualize during rapid skill learning Activities of daily living rely on our ability to acquire new motor skills composed of precise action sequences. Early learning of a new sequential skill is characterized by steep performance improvements that develop predominantly during rest intervals interspersed with practice, a form of rapid consolidation. Here, we ask if the millisecond level neural representation of an action performed at different locations within a skill sequence contextually differentiates or remains stable as learning evolves. Optimization of machine learning decoders to classify sequence-embedded finger movements from MEG activity reached approximately 94% accuracy. The representation manifolds of the same action performed in different sequence contexts progressively differentiated during rest periods of early learning, predicting skill gains. We conclude that sequence action representations contextually differentiate during early skill learning, an issue relevant to brain-computer interface applications in neurorehabilitation.
Functional architecture of cerebral cortex during naturalistic movie watching Characterizing the functional organization of cerebral cortex is a fundamental step in understanding how different kinds of information are processed in the brain. However, it is still unclear how these areas are organized during naturalistic visual and auditory stimulation. Here, we used high-resolution functional MRI data from 176 human subjects to map the macro-architecture of the entire cerebral cortex based on responses to a 60-min audiovisual movie stimulus. A data-driven clustering approach revealed a map of 24 functional areas/networks, each explicitly linked to a specific aspect of sensory or cognitive processing. Novel features of this map included an extended scene-selective network in the lateral prefrontal cortex, separate clusters responsive to human-object and human-human interaction, and a push-pull interaction between three executive control (domain-general) networks and domain-specific regions of the visual, auditory, and language cortex. Our cortical parcellation provides a comprehensive and unified map of functionally defined areas in the human cerebral cortex.
Sex differences in the human brain related to visual motion perception There are sex differences in visuospatial abilities between males and females, including the visual perception of motion information. However, the neural mechanism of these sex differences in motion perception remains yet unclear. To explore this question, we employed the joint task probing motion perception and ultra-high field (UHF) MRI. We found that the motion discrimination was faster in males compared to females. The sex differences were also prominent in major brain parameters in the MT+ region (the function brain regions of motion perception). Males demonstrate (i) larger gray matter volume (GMV) and higher brain’s spontaneous activity in the left MT+ (but not right MT+, i.e., laterality); (ii) stronger functional connectivity between the left MT+ and the left centromedial amygdala (CM). Additionally, we observed that female and male participants exhibited comparable correlations between motion perception ability and the multimodal imaging indexes in the MT+ region, i.e., the larger GMV, the higher brain’s spontaneous activity, and the faster motion discrimination. These results suggest that the sex differences in the structure and function of the MT+ region are the neural mechanism underlying the behavioral-level sex differences in motion perception. We demonstrate sex differences in the healthy human MT+ of the brain, possibly leading to sex differences in visual perception. This strongly support the consideration of sex as a crucial biological variable in both human brain and behavioral research.
High-level visual prediction errors in early visual cortex Perception is shaped by both incoming sensory input and expectations derived from our prior knowledge. Numerous studies have shown stronger neural activity for surprising inputs, suggestive of predictive processing. However, it is largely unclear what predictions are made across the cortical hierarchy, and therefore what kind of surprise drives this up-regulation of activity. Here, we leveraged fMRI in human volunteers and deep neural network (DNN) models to arbitrate between 2 hypotheses: prediction errors may signal a local mismatch between input and expectation at each level of the cortical hierarchy, or prediction errors may be computed at higher levels and the resulting surprise signal is broadcast to earlier areas in the cortical hierarchy. Our results align with the latter hypothesis. Prediction errors in both low- and high-level visual cortex responded to high-level, but not low-level, visual surprise. This scaling with high-level surprise in early visual cortex strongly diverged from feedforward tuning. Combined, our results suggest that high-level predictions constrain sensory processing in earlier areas, thereby aiding perceptual inference.
Functional alterations of the magnocellular subdivision of the visual sensory thalamus in autism The long-standing hypothesis that autism is linked to changes in the visual magnocellular system of the human brain has never been directly examined due to technological constraints. Here, we used a recently developed 7-Tesla functional MRI (fMRI) approach to investigate this hypothesis within the visual sensory thalamus (lateral geniculate nucleus, LGN). The LGN is a crucial component of the primary visual pathway. It is particularly suited to investigate the magnocellular visual system, because within the LGN, the magnocellular (mLGN) uniquely segregates from the parvocellular (pLGN) system. Our results revealed diminished mLGN blood-oxygenation-level-dependent (BOLD) responses in the autism group compared to controls. pLGN responses were comparable across groups. The mLGN alterations were observed specifically for stimuli optimized for mLGN function, i.e., visual displays with low spatial frequency and high temporal flicker frequency. The results confirm the long-standing hypothesis of magnocellular visual system alterations in autism. They substantiate the emerging perspective that sensory processing variations are part of autism symptomatology.