From Observed Action Identity to Social Affordances

A substantial fraction of neurons in the monkey anterior intraparietal area (AIP) and its human homologue phAIP are selective for observed manipulative actions (OMAs).OMA encode identity actions, up to level semantic representation phAIP.OMA may result from combination two visual signals originating superior temporal sulcus (STS) concerning: (i) body movements: (ii) changes hand/object relationship (action effects).Others’ beyond grasping, be specified parietal territories, underpinning ‘social affordance’ processing selection potential behavioral responses parieto-premotor circuits. Others’ cause continuously changing retinal images, making it challenging build neural representations action identity. The putative (phAIP) host (OMAs). neuronal activity both AIP allows a stable readout OMA across formats, but exhibit greater invariance generalize verbs. These properties stem convergence movements; body–object relationship. 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Here, we first review evidence signatures OMA-identity coding brain, point node function. then elucidate connectional architecture enables integration main sources information needed identity: hand–object-interaction (i.e., attainment goal). Finally, extension model larger variety classes ones addition AIP, should drive future studies computation non-human brain. Area has long been considered crucial system routing regarding 3D [18.Murata al.Selectivity shape, size, orientation AIP.J. 2000; 83: 2580-2601Crossref 19.Verhoef B.-E. al.Effects microstimulation three-dimensional Categorization.PLoS One. 2015; 10e0136543Crossref (11) 20.Schaffelhofer Scherberger H. Object vision parietal, premotor, cortices.eLife. 5e15278Crossref (47) Scholar] [21.Pani al.Grasping execution single area.J. 26: 2342-2355Crossref (45) Scholar,22.Maeda K. al.Functional manipulation-related mirror responding own action.J. 560-572Crossref (40) [23.Perrett al.Frameworks analysis animate actions.J. Exp. 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What through achieve actions? study [31.Lanzilotto displayed marked selectivity another grooming) among including emotional gestures lip smacking screaming), neutral yawning chewing), stimuli still monkey, animal, landscape) presented screen. study, also tested large dragging, dropping, pulling, pushing, rotating, squeezing) previously used reveal action-identity addition, four resulting postures actor (standing sitting) viewpoints (lateral frontal) (Figure 1A ). results showed 38% at least format, distinct sets exhibiting preference exemplar (or exemplars), tuning presentation format example Figure 1A). However, no fully visual-invariant found. dynamically according multiplicative mixing described images [32.Ratan Murty N.A. Arun S.P. Multiplicative image attributes 115: E3276-E3285Crossref Such decoding early signal viewpoint (50 ms after stimulus onset) actor’s (at 100 ms) and, slightly later (150 ms), even format-independent manner. Crucially, accuracy decoded depends upon presence subset units maintain relatively formats considerable rescaling firing rate specificities each (as relationship, if exists, between individual AIP? clustering indicated characterized toward lying table (e.g., dragging) closely linked consequently, segregated those already contact manipulated rolling squeezing, 1B). largely independent combinations 1C), suggesting relationships contribution 1A) recently patients participating brain–machine interface clinical trial, allowing researchers record single-neuron rostral [33.Aflalo shared verbs Adv. 6eabb3984Crossref region include [34.Orban G.A. Functional definitions primates.Proc. 283: 1828Google revealed impressive similarities reported monkeys. First, viewpoint, approximately 20% selective, majority them facilitated response 1D), smaller (about 15%) suppressed humans Second, could tuned any tested, coverage uniform Third, population patients, providing significant latency video onset). evident neurons, although difficult reach firm conclusion based available evidence, plausible common ancestor differently sizable OMA-selective exhibited format-invariant (80% invariant 55% invariant), consistent generalization OMA-discrimination tasks [35.Platonov Orban Action observation: less-explored part higher-order vision.Sci. 6: 36742Crossref thus facilitate recruitment reading uniquely capacity. To summarize, primates macaques) remarkably sulcus, variable degree abstraction order access via written words functional basic raise question what anatomical might be. prevalent portion where influence own-hand feedback overall responsiveness found stronger sector tracers injected three positions along rostro-caudal extent physiologically investigated region. confirmed previous [36.Borra connections area.Cereb. 18: 1094-1111Crossref (302) 2A ) quantitative differences connectivity patterns 2B). particular, selectivity, regions, area, occipito-temporal 2C). Although yet neurophysiological lower bank (STS), known target. discharge when isolation some distance other. Furthermore, STS responded similarly many [22.Maeda Scholar,30.Lanzilotto Scholar]; enable assess consequences hand–object interactions. Importantly, unaffected except rigidity food quality. resulted effects essentially rather itself. location corresponds TEa [37.Seltzer B. Pandya D.N. Afferent architectonics surrounding rhesus monkey.Brain Res. 1978; 149: 1-24Crossref (575) prominent projection targeting mainly part, prevail TEa–AIP pathway (red arrow 2C) likely represents source manipulations. Areas IPa/PGa potentially relevant targeted middle-STS [38.Vangeneugden differentiation using parametric space.Cereb. 19: 593-611Crossref (75) features forelimb portrayed stick figures: body-part deformation, encoded ‘snapshot’ kinematic features, ‘motion’ neurons. cells provide rich extracting interactions [39.Sliwa Freiwald dedicated brain.Science. 356: 745-749Crossref (85) Scholar,40.Ong W.S. correlates strategic cooperation monkeys.Nat. 2021; 24: 116-128Crossref constituting key proposed ‘third pathway’ [41.Pitcher D. Ungerleider L.G. 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