1468 Part G Human-Centered and Life-Like Robotics -they will function as labels for components of func-hind which the experimenter is seen to be reaching(see tional systems.To fill in the missing details see,e.g., Umilta et al.[62.105]).All mirror neurons show visual Rizzolatti et al.[62.103,104])A subset of these neu- generalization.They fire when the instrument of the ob- rons,the so-called mirror neurons,also discharge when served action (usually a hand)is large or small,far from the monkey observes meaningful hand movements made or close to the monkey.They may also fire even when by the experimenter which are similar to those whose the action instrument has shapes as different as those of execution is associated with the firing of the neuron.In a human or monkey hand.Some neurons respond even contrast,the canonical neurons are those belonging to when the object is grasped by the mouth.When naive the complementary,anatomically segregated subset of monkeys first see small objects grasped with a pair of grasp-related F5 neurons which fire when the monkey pliers,mirror neurons do not respond,but after exten- performs a specific action and also when it sees an ob- sive training some precision pinch mirror neurons do ject as a possible target of such an action-but do not show activity also to this new grasp type (see Ferrari fire when the monkey sees another monkey or human et al.[62.1061). perform the action.Finally,F5 contains a large popula- Mirror neurons for grasping have also been found in tion of motor neurons which are active when the monkey parietal areas of the macaque brain and,recently,it has grasps an object(either with the hand or mouth)but do been shown that parietal mirror neurons are sensitive not possess any visual response.F5 is clearly a motor to the context of the observed action being predictive area although the details of the muscular activation are of the outcome as a function of contextual cues-e.g., abstracted out-F5 neurons can be effector-independent.some grasp-related parietal mirror neurons may fire for In contrast,the primary motor cortex(Fl)formulates a grasp that precedes eating the grasped object while the neural instructions for lower motor areas and motor others fire for a grasp that precedes placing the object neurons. in a container (see Fogassi et al.[62.1071).In practice Moreover,macaque mirror neurons encode transitive the parieto-frontal circuitry seems to encode action exe- actions and do not fire when the monkey sees the hand cution and simultaneously action recognition by taking movement unless it can also see the object or,more sub- into account a large set of potential candidate actions tly,if the object is not visible but is appropriately located which are selected on the basis of a range of cues such in working memory because it has recently been placed as vision of the relation of the effector to the object on a surface and has then been obscured by a screen be- and certain sounds(when relevant for the task).Further, feedback connections (frontal to parietal)are thought to be part of a stimulus selection process which refines the clPS AIP sensory processing by attending to stimuli relevant for Modulating choice of affordances the ongoing action (see Rizzolatti et al.[62.62]and re- call the discussion in Sect.62.2.5).Recognition is then supported by the activation of the same circuitry in the PFC Working memory (46) absence of overt movement. Instruction stimuli(F2) We clarify these ideas by briefly presenting the FARS Pre-SMA(F6) When to more model of the canonical F5 neurons and the MNS model sequence organization of the F5 mirror neurons.In each case.the F5 neu- Affordances Part Visual input "G0 rons function effectively only because of the interaction signal" of F5 with a wide range of other regions.We have stressed(Sect.62.2.3)the distinction between recogni- Motor Fl Motor Premotor F5 2.4 schema tion of the category of an object and recognition of its (Canonical) affordances.The parietal area AIP processes visual in- Ventral stream T formation to extract affordances,in this case properties "ltr's a mug'” of the object relevant to grasping it (Tairaet al.[62.1081). Hand control AIP and F5 are reciprocally connected,with AIP being Fig.62.6 The original FARS diagram(see Fagg and Arbib [62.45]) more visual and F5 more motoric. is here modified to show PFC acting on AlP rather than F5.The idea The Fagg-Arbib-Rizzolatti-Sakata (FARS)model is that the prefrontal cortex uses the IT identification of the object, (see Fagg and Arbib [62.109]and Fig.62.6)embeds in concert with task analysis and working memory,to help the AIP F5 canonical neurons in a larger system.The dorsal select the appropriate affordance from its menu stream(which passes through AIP)can only analyze the1468 Part G Human-Centered and Life-Like Robotics – they will function as labels for components of func￾tional systems. To fill in the missing details see, e.g., Rizzolatti et al. [62.103, 104]) A subset of these neu￾rons, the so-called mirror neurons, also discharge when the monkey observes meaningful hand movements made by the experimenter which are similar to those whose execution is associated with the firing of the neuron. In contrast, the canonical neurons are those belonging to the complementary, anatomically segregated subset of grasp-related F5 neurons which fire when the monkey performs a specific action and also when it sees an ob￾ject as a possible target of such an action – but do not fire when the monkey sees another monkey or human perform the action. Finally, F5 contains a large popula￾tion of motor neurons which are active when the monkey grasps an object (either with the hand or mouth) but do not possess any visual response. F5 is clearly a motor area although the details of the muscular activation are abstracted out – F5 neurons can be effector-independent. In contrast, the primary motor cortex (F1) formulates the neural instructions for lower motor areas and motor neurons. Moreover, macaque mirror neurons encode transitive actions and do not fire when the monkey sees the hand movement unless it can also see the object or, more sub￾tly, if the object is not visible but is appropriately located in working memory because it has recently been placed on a surface and has then been obscured by a screen be￾Modulating choice of affordances Affordances Motor schema Hand control Visual input "It's a mug" IT PFC AIP Motor F1 Premotor F5 (Canonical) cIPS "Go signal" Working memory (46) Instruction stimuli (F2) Pre-SMA (F6) When to move sequence organization Ventral stream: Recognition Dorsal stream: Affordances Fig. 62.6 The original FARS diagram (see Fagg and Arbib [62.45]) is here modified to show PFC acting on AIP rather than F5. The idea is that the prefrontal cortex uses the IT identification of the object, in concert with task analysis and working memory, to help the AIP select the appropriate affordance from its menu hind which the experimenter is seen to be reaching (see Umilta` et al. [62.105]). All mirror neurons show visual generalization. They fire when the instrument of the ob￾served action (usually a hand) is large or small, far from or close to the monkey. They may also fire even when the action instrument has shapes as different as those of a human or monkey hand. Some neurons respond even when the object is grasped by the mouth. When naive monkeys first see small objects grasped with a pair of pliers, mirror neurons do not respond, but after exten￾sive training some precision pinch mirror neurons do show activity also to this new grasp type (see Ferrari et al. [62.106]). Mirror neurons for grasping have also been found in parietal areas of the macaque brain and, recently, it has been shown that parietal mirror neurons are sensitive to the context of the observed action being predictive of the outcome as a function of contextual cues – e.g., some grasp-related parietal mirror neurons may fire for a grasp that precedes eating the grasped object while others fire for a grasp that precedes placing the object in a container (see Fogassi et al. [62.107]). In practice the parieto-frontal circuitry seems to encode action exe￾cution and simultaneously action recognition by taking into account a large set of potential candidate actions which are selected on the basis of a range of cues such as vision of the relation of the effector to the object and certain sounds (when relevant for the task). Further, feedback connections (frontal to parietal) are thought to be part of a stimulus selection process which refines the sensory processing by attending to stimuli relevant for the ongoing action (see Rizzolatti et al. [62.62] and re￾call the discussion in Sect. 62.2.5). Recognition is then supported by the activation of the same circuitry in the absence of overt movement. We clarify these ideas by briefly presenting the FARS model of the canonical F5 neurons and the MNS model of the F5 mirror neurons. In each case, the F5 neu￾rons function effectively only because of the interaction of F5 with a wide range of other regions. We have stressed (Sect. 62.2.3) the distinction between recogni￾tion of the category of an object and recognition of its affordances. The parietal area AIP processes visual in￾formation to extract affordances, in this case properties of the object relevant to grasping it (Taira et al. [62.108]). AIP and F5 are reciprocally connected, with AIP being more visual and F5 more motoric. The Fagg–Arbib–Rizzolatti–Sakata (FARS) model (see Fagg and Arbib [62.109] and Fig. 62.6) embeds F5 canonical neurons in a larger system. The dorsal stream (which passes through AIP) can only analyze the Part G 62.4