Decision making involves dynamic interplay between internal judgements and external perception, which has been investigated in delayed match-to-category (DMC) experiments. Our analysis of neural ...recordings shows that, during DMC tasks, LIP and PFC neurons demonstrate mixed, time-varying, and heterogeneous selectivity, but previous theoretical work has not established the link between these neural characteristics and population-level computations. We trained a recurrent network model to perform DMC tasks and found that the model can remarkably reproduce key features of neuronal selectivity at the single-neuron and population levels. Analysis of the trained networks elucidates that robust transient trajectories of the neural population are the key driver of sequential categorical decisions. The directions of trajectories are governed by network self-organized connectivity, defining a “neural landscape” consisting of a task-tailored arrangement of slow states and dynamical tunnels. With this model, we can identify functionally relevant circuit motifs and generalize the framework to solve other categorization tasks.
•Recurrent networks trained to perform DMC tasks exhibit robust transience dynamics•Dynamics consist of stable and slow states connected by robust trajectory tunnels•Models’ neural activities are remarkably similar to recordings from LIP and PFC•Trained RNNs replicate categorization studies with multiple categories
Chaisangmongkon et al. present a recurrent neural network model of primate fronto-parietal network that can capture various phenomena from neurophysiological experiments in delayed match-to-category tasks.
The ability to recognize the behavioral relevance, or category membership, of sensory stimuli is critical for interpreting the meaning of events in our environment. Neurophysiological studies of ...visual categorization have found categorical representations of stimuli in prefrontal cortex (PFC), an area that is closely associated with cognitive and executive functions. Recent studies have also identified neuronal category signals in parietal areas that are typically associated with visual-spatial processing. It has been proposed that category-related signals in parietal cortex and other visual areas may result from 'top-down' feedback from PFC. We directly compared neuronal activity in the lateral intraparietal (LIP) area and PFC in monkeys performing a visual motion categorization task. We found that LIP showed stronger, more reliable and shorter latency category signals than PFC. These findings suggest that LIP is strongly involved in visual categorization and argue against the idea that parietal category signals arise as a result of feedback from PFC during this task.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Comparing sequential stimuli is crucial for guiding complex behaviors. To understand mechanisms underlying sequential decisions, we compared neuronal responses in the prefrontal cortex (PFC), the ...lateral intraparietal (LIP), and medial intraparietal (MIP) areas in monkeys trained to decide whether sequentially presented stimuli were from matching (M) or nonmatching (NM) categories. We found that PFC leads M/NM decisions, whereas LIP and MIP appear more involved in stimulus evaluation and motor planning, respectively. Compared to LIP, PFC showed greater nonlinear integration of currently visible and remembered stimuli, which correlated with the monkeys' M/NM decisions. Furthermore, multi-module recurrent networks trained on the same task exhibited key features of PFC and LIP encoding, including nonlinear integration in the PFC-like module, which was causally involved in the networks' decisions. Network analysis found that nonlinear units have stronger and more widespread connections with input, output, and within-area units, indicating putative circuit-level mechanisms for sequential decisions.
Little is known about the architecture of cellular microenvironments that support stem and precursor cells during tissue development. Although adult stem cell niches are organized by specialized ...supporting cells, in the developing cerebral cortex, neural stem/precursor cells reside in a neurogenic niche lacking distinct supporting cells. Here, we find that neural precursors themselves comprise the niche and regulate their own development. Precursor-precursor contact regulates β-catenin signaling and cell fate. In vivo knockdown of N-cadherin reduces β-catenin signaling, migration from the niche, and neuronal differentiation in vivo. N-cadherin engagement activates β-catenin signaling via Akt, suggesting a mechanism through which cells in tissues can regulate their development. These results suggest that neural precursor cell interactions can generate a self-supportive niche to regulate their own number.
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► Cortical ventricular zone neural precursors exhibit β-catenin signaling ► N-cadherin maintains β-catenin signaling in cortical precursors ► N-cadherin regulates neuronal differentiation and cell cycle exit via β-catenin ► N-cadherin signals through Akt and phosphor-Ser552 of β-catenin
Categorization is essential for interpreting sensory stimuli and guiding our actions. Recent studies have revealed robust neuronal category representations in the lateral intraparietal area (LIP). ...Here, we examine the specialization of LIP for categorization and the roles of other parietal areas by comparing LIP and the medial intraparietal area (MIP) during a visual categorization task. MIP is involved in goal-directed arm movements and visuomotor coordination but has not been implicated in non-motor cognitive functions, such as categorization. As expected, we found strong category encoding in LIP. Interestingly, we also observed category signals in MIP. However, category signals were stronger and appeared with a shorter latency in LIP than MIP. In this task, monkeys indicated whether a test stimulus was a category match to a previous sample with a manual response. Test-period activity in LIP showed category encoding and distinguished between matches and non-matches. In contrast, MIP primarily reflected the match/non-match status of test stimuli, with a strong preference for matches (which required a motor response). This suggests that, although category representations are distributed across parietal cortex, LIP and MIP play distinct roles: LIP appears more involved in the categorization process itself, whereas MIP is more closely tied to decision-related motor actions.
Visual categorization and the parietal cortex Fitzgerald, Jamie K; Swaminathan, Sruthi K; Freedman, David J
Frontiers in integrative neuroscience,
01/2012, Letnik:
6
Journal Article
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The primate brain is adept at rapidly grouping items and events into functional classes, or categories, in order to recognize the significance of stimuli and guide behavior. Higher cognitive ...functions have traditionally been considered the domain of frontal areas. However, increasing evidence suggests that parietal cortex is also involved in categorical and associative processes. Previous work showed that the parietal cortex is highly involved in spatial processing, attention, and saccadic eye movement planning, and more recent studies have found decision-making signals in lateral intraparietal area (LIP). We recently found that a subdivision of parietal cortex, LIP, reflects learned categories for multiple types of visual stimuli. Additionally, a comparison of categorization signals in parietal and frontal areas found stronger and earlier categorization signals in parietal cortex arguing that, in trained animals, parietal abstract association or category signals are unlikely to arise via feedback from prefrontal cortex (PFC).
The ability to recognize the behavioral significance, or category membership, of sensory stimuli is critical for interpreting the meaning of events in our environment. Prior neurophysiological ...studies of visual categorization found categorical representations of stimuli in prefrontal cortex (PFC), an area closely associated with cognitive and executive functions. Recent studies have also identified neuronal category signals in parietal areas typically associated with visual-spatial processing. It has been proposed that category-related signals in parietal cortex and other visual areas may result from “top-down” feedback from PFC. We directly compared neuronal activity in the lateral intraparietal (LIP) area and PFC in monkeys performing a visual motion categorization task. Here we show that LIP shows stronger, more reliable, and shorter latency category signals than PFC. This suggests that LIP is strongly involved in visual categorization, and argues against the idea that parietal category signals arise from feedback from PFC during this task.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Little is known about the architecture of cellular microenvironments that support stem and precursor cells during tissue development. Although adult stem cell niches are organized by specialized ...supporting cells, in the developing cerebral cortex, neural stem/precursor cells reside in a neurogenic niche lacking distinct supporting cells. Here, we find that neural precursors themselves comprise the niche and regulate their own development. Precursor-precursor contact regulates b-catenin signaling and cell fate. In vivo knockdown of N-cadherin reduces b-catenin signaling, migration from the niche, and neuronal differentiation in vivo. N-cadherin engagement activates b-catenin signaling via Akt, suggesting a mechanism through which cells in tissues can regulate their development. These results suggest that neural precursor cell interactions can generate a self-supportive niche to regulate their own number. Highlights - Cortical ventricular zone neural precursors exhibit b-catenin signaling N-cadherin maintains b-catenin signaling in cortical precursors N-cadherin regulates neuronal differentiation and cell cycle exit via b-catenin N-cadherin signals through Akt and phosphor-Ser552 of b-catenin
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