Sequential neuronal processing of number values, abstract decision, and action in the primate prefrontal cortex.

Decision-making requires processing of sensory information, comparing the gathered evidence to make a judgment, and performing the action to communicate it. How neuronal representations transform during this cascade of representations remains a matter of debate. Here, we studied the succession of neuronal representations in the primate prefrontal cortex (PFC). We trained monkeys to judge whether a pair of sequentially presented displays had the same number of items. We used a combination of single neuron and population-level analyses and discovered a sequential transformation of represented information with trial progression. While numerical values were initially represented with high precision and in conjunction with detailed information such as order, the decision was encoded in a low-dimensional subspace of neural activity. This decision encoding was invariant to both retrospective numerical values and prospective motor plans, representing only the binary judgment of "same number" versus "different number," thus facilitating the generalization of decisions to novel number pairs. We conclude that this transformation of neuronal codes within the prefrontal cortex supports cognitive flexibility and generalizability of decisions to new conditions.

Blind spot sensor systems for power wheelchairs: obstacle detection accuracy, cognitive task load, and perceived usefulness among older adults.

PURPOSE: Blind spot sensor systems can improve power wheelchair (PWC) safety. This research (1) compared accuracy of obstacle detection in the rear of a wheelchair with and without a sensor system, and (2) explored cognitive task load and perceived usability, safety, confidence and awareness in a laboratory setting, and (3) PWC users' perceptions in real-world settings. MATERIALS AND METHODS: A mixed-method design was used. PWC users were provided with the sensor system. In laboratory accuracy of obstacle detection with and without a sensor system, cognitive task load and perceived usability, safety, confidence and awareness were evaluated. Participants then used the sensor system at home for two-months before completing semi-structured interviews. Statistical and thematic analyses were conducted. RESULTS: Among 11 PWC users (age = 67.5 ± 7.5y), obstacles were detected more accurately with sensor system than without (p < 0.001). Using the sensor system required lower cognitive task loads (p = 0.005). The system was perceived by most users as easy to use (9/11) and its capabilities meeting their requirements (8/11). Most users did not perceive safety (9/11), confidence (9/11) or increased awareness (10/11) in the laboratory. Three themes emerged in the follow-ups: perceived usefulness, barriers to use, and recommendations. Four participants reported continued use after 2 months, reporting perceived increased awareness, convenience, and independence using the system. Those who discontinued use reported perceived lack of usefulness and technical issues. Recommendations included types of users who can benefit and sensor improvements. CONCLUSIONS: Sensor systems may improve obstacle detection accuracy while reducing cognitive task load. However, larger scale implementation should consider recommendations for PWC service provision.IMPLICATIONS FOR REHABILITATIONBlind spot sensors systems increased speed and accuracy of obstacle detection when using a power wheelchair.Technical and hardware issues encountered by PWC users highlight the need for training and support services.Technical support was out of scope for the current research project and will be explored in future research given the critical role it might play in the usability and adoption of assistive technologies.PWC users perceived there to be practical uses for blind spot sensor systems.

A fast link between face perception and memory in the temporal pole.

The question of how the brain recognizes the faces of familiar individuals has been important throughout the history of neuroscience. Cells linking visual processing to person memory have been proposed but not found. Here, we report the discovery of such cells through recordings from an area in the macaque temporal pole identified with functional magnetic resonance imaging. These cells responded to faces that were personally familiar. They responded nonlinearly to stepwise changes in face visibility and detail and holistically to face parts, reflecting key signatures of familiar face recognition. They discriminated between familiar identities, as fast as a general face identity area. The discovery of these cells establishes a new pathway for the fast recognition of familiar individuals.

The Time Is Now: A FASTER Approach to Generate Research Evidence for Technology-Based Interventions in the Field of Disability and Rehabilitation.

Current approaches for generating high-quality research evidence for technology-based interventions in the field of disability and rehabilitation are inappropriate. Prevailing approaches often focus on randomized controlled trials as standard and apply clinical trial practices designed for pharmaceuticals; such approaches are unsuitable for technology-based interventions and are counterproductive to the goals of supporting people with disabilities and creating benefits for society. This communication is designed to: (1) advocate for the use of alternative approaches to generating evidence in the development and evaluation of technology-based interventions; (2) propose an alternative framework and guiding principles; and (3) stimulate action by multiple disciplines and sectors to discuss, adopt, and promote alternative approaches. Our Framework for Accelerated and Systematic Technology-based intervention development and Evaluation Research (FASTER) is informed by established innovation design processes, complex intervention development, evaluation, and implementation concepts as well as our collective experiences in technology-based interventions research and clinical rehabilitation practice. FASTER is intended to be meaningful, timely, and practical for researchers, technology developers, clinicians, and others who develop these interventions and seek evidence. We incorporate research methods and designs that better align with creating technology-based interventions and evidence for integration into practice. We propose future activities to improve the generation of research evidence, enable the selection of research methods and designs, and create standards for evidence evaluation to support rigor and applicability for technology-based interventions. With this communication we aim to improve and advance technology-based intervention integration from conception to use, thus responsibly accelerating innovation to have greater positive benefit for people and society.

Spatial Neuronal Integration Supports a Global Representation of Visual Numerosity in Primate Association Cortices.

Our sense of number rests on the activity of neurons that are tuned to the number of items and show great invariance across display formats and modalities. Whether numerosity coding becomes abstracted from local spatial representations characteristic of visual input is not known. We mapped the visual receptive fields (RFs) of numerosity-selective neurons in the pFC and ventral intraparietal area in rhesus monkeys. We found numerosity selectivity in pFC and ventral intraparietal neurons irrespective of whether they exhibited an RF and independent of the location of their RFs. RFs were not predictive of the preference of numerosity-selective neurons. Furthermore, the presence and location of RFs had no impact on tuning width and quality of the numerosity-selective neurons. These findings show that neurons in frontal and parietal cortices integrate abstract visuospatial stimuli to give rise to global and spatially released number representations as required for number perception.

Number detectors spontaneously emerge in a deep neural network designed for visual object recognition.

Humans and animals have a "number sense," an innate capability to intuitively assess the number of visual items in a set, its numerosity. This capability implies that mechanisms to extract numerosity indwell the brain's visual system, which is primarily concerned with visual object recognition. Here, we show that network units tuned to abstract numerosity, and therefore reminiscent of real number neurons, spontaneously emerge in a biologically inspired deep neural network that was merely trained on visual object recognition. These numerosity-tuned units underlay the network's number discrimination performance that showed all the characteristics of human and animal number discriminations as predicted by the Weber-Fechner law. These findings explain the spontaneous emergence of the number sense based on mechanisms inherent to the visual system.

Comparison of visual receptive fields in the dorsolateral prefrontal cortex and ventral intraparietal area in macaques.

The concept of receptive field (RF) describes the responsiveness of neurons to sensory space. Neurons in the primate association cortices have long been known to be spatially selective but a detailed characterisation and direct comparison of RFs between frontal and parietal association cortices are missing. We sampled the RFs of a large number of neurons from two interconnected areas of the frontal and parietal lobes, the dorsolateral prefrontal cortex (dlPFC) and ventral intraparietal area (VIP), of rhesus monkeys by systematically presenting a moving bar during passive fixation. We found that more than half of neurons in both areas showed spatial selectivity. Single neurons in both areas could be assigned to five classes according to the spatial response patterns: few non-uniform RFs with multiple discrete response maxima could be dissociated from the vast majority of uniform RFs showing a single maximum; the latter were further classified into full-field and confined foveal, contralateral and ipsilateral RFs. Neurons in dlPFC showed a preference for the contralateral visual space and collectively encoded the contralateral visual hemi-field. In contrast, VIP neurons preferred central locations, predominantly covering the foveal visual space. Putative pyramidal cells with broad-spiking waveforms in PFC had smaller RFs than putative interneurons showing narrow-spiking waveforms, but distributed similarly across the visual field. In VIP, however, both putative pyramidal cells and interneurons had similar RFs at similar eccentricities. We provide a first, thorough characterisation of visual RFs in two reciprocally connected areas of a fronto-parietal cortical network.

Visual Receptive Field Heterogeneity and Functional Connectivity of Adjacent Neurons in Primate Frontoparietal Association Cortices.

The basic organization principles of the primary visual cortex (V1) are commonly assumed to also hold in the association cortex such that neurons within a cortical column share functional connectivity patterns and represent the same region of the visual field. We mapped the visual receptive fields (RFs) of neurons recorded at the same electrode in the ventral intraparietal area (VIP) and the lateral prefrontal cortex (PFC) of rhesus monkeys. We report that the spatial characteristics of visual RFs between adjacent neurons differed considerably, with increasing heterogeneity from VIP to PFC. In addition to RF incongruences, we found differential functional connectivity between putative inhibitory interneurons and pyramidal cells in PFC and VIP. These findings suggest that local RF topography vanishes with hierarchical distance from visual cortical input and argue for increasingly modified functional microcircuits in noncanonical association cortices that contrast V1.SIGNIFICANCE STATEMENT Our visual field is thought to be represented faithfully by the early visual brain areas; all the information from a certain region of the visual field is conveyed to neurons situated close together within a functionally defined cortical column. We examined this principle in the association areas, PFC, and ventral intraparietal area of rhesus monkeys and found that adjacent neurons represent markedly different areas of the visual field. This is the first demonstration of such noncanonical organization of these brain areas.

Intelligent power wheelchair use in long-term care: potential users' experiences and perceptions.

PURPOSE: Long-term care (LTC) residents with cognitive impairments frequently experience limited mobility and participation in preferred activities. Although a power wheelchair could mitigate some of these mobility and participation challenges, this technology is often not prescribed for this population due to safety concerns. An intelligent power wheelchair (IPW) system represents a potential intervention that could help to overcome these concerns. The purpose of this study was to explore a) how residents experienced an IPW that used three different modes of control and b) what perceived effect the IPW would have on their daily lives. MATERIALS AND METHODS: We interviewed 10 LTC residents with mild or moderate cognitive impairment twice, once before and once after testing the IPW. Interviews were conducted using a semi-structured interview guide, audio recorded and transcribed verbatim for thematic analyses. RESULTS: Our analyses identified three overarching themes: (1) the difference an IPW would make, (2) the potential impact of the IPW on others and (3) IPW-related concerns. CONCLUSIONS: Findings from this study confirm the need for and potential benefits of IPW use in LTC. Future studies will involve testing IPW improvements based on feedback and insights from this study. Implications for rehabilitation Intelligent power wheelchairs may enhance participation and improve safety and feelings of well-being for long-term care residents with cognitive impairments. Intelligent power wheelchairs could potentially have an equally positive impact on facility staff, other residents, and family and friends by decreasing workload and increasing safety.

Differential impact of behavioral relevance on quantity coding in primate frontal and parietal neurons.

Prefrontal cortex (PFC) and posterior parietal cortex are key brain areas for magnitude representations. Whether active discrimination of numerosity changes neuronal representations is still not known. We simultaneously recorded from the same recording sites in the PFC and ventral intraparietal area (VIP) before and after monkeys learned to actively discriminate the number of items in a set. Only PFC neurons, and not VIP neurons, exhibited heightened representation of number after numerosity training. Increased responsiveness of PFC was evidenced by enhanced differentiation of numerosity by the population of neurons, as well as increased numerosity encoding by individual selective neurons. None of these effects were observed in the VIP, in which neurons responded invariably to numerosity irrespective of behavioral relevance. This suggests elevated PFC participation during numerical task demands and executive control, whereas VIP encodes quantity as a perceptual category regardless of behavioral relevance.

A common stochastic accumulator with effector-dependent noise can explain eye-hand coordination.

The computational architecture that enables the flexible coupling between otherwise independent eye and hand effector systems is not understood. By using a drift diffusion framework, in which variability of the reaction time (RT) distribution scales with mean RT, we tested the ability of a common stochastic accumulator to explain eye-hand coordination. Using a combination of behavior, computational modeling and electromyography, we show how a single stochastic accumulator to threshold, followed by noisy effector-dependent delays, explains eye-hand RT distributions and their correlation, while an alternate independent, interactive eye and hand accumulator model does not. Interestingly, the common accumulator model did not explain the RT distributions of the same subjects when they made eye and hand movements in isolation. Taken together, these data suggest that a dedicated circuit underlies coordinated eye-hand planning.

Neuronal correlates of a visual "sense of number" in primate parietal and prefrontal cortices.

"Sense of number" refers to the classical idea that we perceive the number of items (numerosity) intuitively. However, whether the brain signals numerosity spontaneously, in the absence of learning, remains unknown; therefore, we recorded from neurons in the ventral intraparietal sulcus and the dorsolateral prefrontal cortex of numerically naive monkeys. Neurons in both brain areas responded maximally to a given number of items, showing tuning to a preferred numerosity. Numerosity was encoded earlier in area ventral intraparietal area, suggesting that numerical information is conveyed from the parietal to the frontal lobe. Visual numerosity is thus spontaneously represented as a perceptual category in a dedicated parietofrontal network. This network may form the biological foundation of a spontaneous number sense, allowing primates to intuitively estimate the number of visual items.