Neural correlates of hand-tool interaction

Background: The recent advent of non-invasive functional magnetic resonance image (fMRI) has helped us understand how visual information is processed in the visual system, and the functional organising principles of high-order visual areas beyond striate cortex. In particular, evidence has been reported for a constellation of high-order visual areas that are highly specialised for the visual processing of different object domains such as faces, bodies, and tools. A number of accounts of the underlying principle of functional specialisation in high-order visual cortex propose that visual properties and object domain drive the category selectivity of these areas. However, recent evidence has challenged such accounts, showing that non-visual object properties and connectivity constraints between specialised brain networks can, in part, account for the visual system’s functional organisation. Methodology: Here I will use fMRI to examine how areas along the visual ventral stream and dorsal action stream process visually presented hands and tools. These categories are visually dissimilar but share similar functions. By using different statistical analyses, such as univariate group and single-subject region of interest (ROI) analyses, multivariate multivoxel pattern analyses, and functional connectivity analyses, I will investigate the topics of category-selectivity and the principles underlying the organisation of high-order visual areas in left occipitotemporal and left parietal cortex. Principle Findings: In the first part of this thesis I report novel evidence that, similar to socially relevant faces and bodies, the human high-order visual areas in left occipitotemporal and left parietal cortex houses areas that are selective for the visual processing of human hands. In the second part of this thesis, I show that the visual representation of hands and tools in these areas show large anatomical overlap and high similarity in the response patterns to these categories. As hands and tools differ in visual appearance and object domain yet share action-related properties, the results demonstrate that these category-selective responses in the visual system reflect responses to non-visual action-related object properties common to hands and tools rather than to purely visual properties or object domain. This proposition is further supported by evidence of selective functional connectivity patterns between hand/tool occipitotemporal and parietal areas. Conclusions/Significance: Overall these results indicate that high-order visual cortex is functionally organised to process both visual properties and non-visual object dimensions (e.g., action-related properties). I propose that this correspondence between hand and tool representations in ventral ‘visual’ and parietal ‘action’ areas is constrained by the necessity to connect visual object information to functionally-specific downstream networks (e.g., frontoparietal action network) to facilitate hand-tool action-related processing

Tool Selectivity in Left Occipitotemporal Cortex Develops without Vision

Previous studies have provided evidence for a tool-selective region in left lateral occipitotemporal cortex (LOTC). This region responds selectively to pictures of tools and to characteristic visual tool motion. The present human fMRI study tested whether visual experience is required for the development of tool-selective responses in left LOTC. Words referring to tools, animals, and nonmanipulable objects were presented auditorily to 14 congenitally blind and 16 sighted participants. Sighted participants additionally viewed pictures of these objects. In whole-brain group analyses, sighted participants showed tool-selective activity in left LOTC in both visual and auditory tasks. Importantly, virtually identical tool-selective LOTC activity was found in the congenitally blind group performing the auditory task. Furthermore, both groups showed equally strong tool-selective activity for auditory stimuli in a tool-selective LOTC region defined by the picture-viewing task in the sighted group. Detailed analyses in individual participants showed significant tool-selective LOTC activity in 13 of 14 blind participants and 14 of 16 sighted participants. The strength and anatomical location of this activity were indistinguishable across groups. Finally, both blind and sighted groups showed significant resting state functional connectivity between left LOTC and a bilateral frontoparietal network. Together, these results indicate that tool-selective activity in left LOTC develops without ever having seen a tool or its motion. This finding puts constraints on the possible role that this region could have in tool processing and, more generally, provides new insights into the principles shaping the functional organization of OTC.Psycholog

Neural correlates of hand-tool interaction

Background: The recent advent of non-invasive functional magnetic resonance image (fMRI) has helped us understand how visual information is processed in the visual system, and the functional organising principles of high-order visual areas beyond striate cortex. In particular, evidence has been reported for a constellation of high-order visual areas that are highly specialised for the visual processing of different object domains such as faces, bodies, and tools. A number of accounts of the underlying principle of functional specialisation in high-order visual cortex propose that visual properties and object domain drive the category selectivity of these areas. However, recent evidence has challenged such accounts, showing that non-visual object properties and connectivity constraints between specialised brain networks can, in part, account for the visual system’s functional organisation. Methodology: Here I will use fMRI to examine how areas along the visual ventral stream and dorsal action stream process visually presented hands and tools. These categories are visually dissimilar but share similar functions. By using different statistical analyses, such as univariate group and single-subject region of interest (ROI) analyses, multivariate multivoxel pattern analyses, and functional connectivity analyses, I will investigate the topics of category-selectivity and the principles underlying the organisation of high-order visual areas in left occipitotemporal and left parietal cortex. Principle Findings: In the first part of this thesis I report novel evidence that, similar to socially relevant faces and bodies, the human high-order visual areas in left occipitotemporal and left parietal cortex houses areas that are selective for the visual processing of human hands. In the second part of this thesis, I show that the visual representation of hands and tools in these areas show large anatomical overlap and high similarity in the response patterns to these categories. As hands and tools differ in visual appearance and object domain yet share action-related properties, the results demonstrate that these category-selective responses in the visual system reflect responses to non-visual action-related object properties common to hands and tools rather than to purely visual properties or object domain. This proposition is further supported by evidence of selective functional connectivity patterns between hand/tool occipitotemporal and parietal areas. Conclusions/Significance: Overall these results indicate that high-order visual cortex is functionally organised to process both visual properties and non-visual object dimensions (e.g., action-related properties). I propose that this correspondence between hand and tool representations in ventral ‘visual’ and parietal ‘action’ areas is constrained by the necessity to connect visual object information to functionally-specific downstream networks (e.g., frontoparietal action network) to facilitate hand-tool action-related processing.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Neural correlates of hand–object congruency effects during action planning

Selecting hand actions to manipulate an object is affected both by perceptual factors and by action goals. Affordances may contribute to “stimulus–response” congruency effects driven by habitual actions to an object. In previous studies, we have demonstrated an influence of the congruency between hand and object orientations on response times when reaching to turn an object, such as a cup. In this study, we investigated how the representation of hand postures triggered by planning to turn a cup was influenced by this congruency effect, in an fMRI scanning environment. Healthy participants were asked to reach and turn a real cup that was placed in front of them either in an upright orientation or upside–down. They were instructed to use a hand orientation that was either congruent or incongruent with the cup orientation. As expected, the motor responses were faster when the hand and cup orientations were congruent. There was increased activity in a network of brain regions involving object-directed actions during action planning, which included bilateral primary and extrastriate visual, medial, and superior temporal areas, as well as superior parietal, primary motor, and premotor areas in the left hemisphere. Specific activation of the dorsal premotor cortex was associated with hand–object orientation congruency during planning and prior to any action taking place. Activity in that area and its connectivity with the lateral occipitotemporal cortex increased when planning incongruent (goal-directed) actions. The increased activity in premotor areas in trials where the orientation of the hand was incongruent to that of the object suggests a role in eliciting competing representations specified by hand postures in lateral occipito-temporal cortex

Characterization of snowfall estimated by in situ and ground-based remote-sensing observations at Terra Nova Bay, Victoria Land, Antarctica

AbstractKnowledge of the precipitation contribution to the Antarctic surface mass balance is essential for defining the ice-sheet contribution to sea-level rise. Observations of precipitation are sparse over Antarctica, due to harsh environmental conditions. Precipitation during the summer months (November–December–January) on four expeditions, 2015–16, 2016–17, 2017–18 and 2018–19, in the Terra Nova Bay area, were monitored using a vertically pointing radar, disdrometer, snow gauge, radiosounding and an automatic weather station installed at the Italian Mario Zucchelli Station. The relationship between radar reflectivity and precipitation rate at the site can be estimated using these instruments jointly. The error in calculated precipitation is up to 40%, mostly dependent on reflectivity variability and disdrometer inability to define the real particle fall velocity. Mean derived summer precipitation is ~55 mm water equivalent but with a large variability. During collocated measurements in 2018–19, corrected snow gauge amounts agree with those derived from the relationship, within the estimated errors. European Centre for the Medium-Range Weather Forecasts (ECMWF) and the Antarctic Mesoscale Prediction System (AMPS) analysis and operational outputs are able to forecast the precipitation timing but do not adequately reproduce quantities during the most intense events, with overestimation for ECMWF and underestimation for AMPS

View-invariant representation of hand postures in the human lateral occipitotemporal cortex

Understanding other people's actions and mental states includes the interpretation of body postures and movements. In particular, hand postures are an important channel to signal both action and communicative intentions. Recognizing hand postures is computationally challenging because hand postures often differ only in the subtle configuration of relative finger positions and because visual characteristics of hand postures change across viewpoints. To allow for accurate interpretation, the brain needs to represent hand postures in a view-invariant but posture-specific manner. Here we test for such representations in hand-, body-, and object-selective regions of the lateral occipitotemporal cortex (LOTC). We used multivariate pattern analysis of fMRI data to test for view-specific and view-invariant representations of individual hand postures, separately for two domains: action-related postures (e.g., a precision grasp) and communicative postures (e.g., thumbs up). Results showed that hand-selective LOTC, but not nearby body- and object-selective LOTC, represented hand postures in a view-invariant manner, with relatively similar activity patterns to the same hand posture seen from different viewpoints. View invariance was equally strong for action and communicative postures. By contrast, object-selective cortex represented hand postures in a view-specific manner. These results indicate a role for hand-selective LOTC in solving the view-invariance problem for individual hand postures. View-invariant representations of hand postures in this region may then be accessed and further interpreted by multiple downstream systems to inform high-level judgments related to action understanding, emotion recognition, and non-verbal communication.status: publishe