Eye-hand interactions in tracing and drawing tasks

We report a preliminary analysis of the interactions between eye and hand during tracing and drawing of four simple shapes. Eye and hand movements were recorded using the ASL 504 system and the Flock of Birds system, respectively. During tracing, pen tip and eye were tightly coupled, with participants making a series of small saccades just in front of the moving pen, interspersed with periods of smooth pursuit. During drawing, saccades were fewer and larger and pursuit was less frequent. Observed eye-hand interactions suggested a bidirectional relationship between the eye and hand. These findings are explained in terms of the differing degree that the two tasks employ visual detail, external or internal cues and eye-hand coordination.     

Superior parietal cortices and varieties of mental rotation

Mental rotation is the most distinctly specialized operation of the imagination, one characterized precisely enough psychophysically for parametric study, thereby making it an optimal prospect for isolating and modeling its neural mechanisms. New human brain mapping studies using direct cortical stimulation and repetitive transcranial magnetic stimulation isolate an area in right superior parietal cortex that appears to be crucial for the mental rotation of objects, but not to the mental rotation of one's body.     

Differential roles of the frontal and parietal cortices in the control of saccades

Although externally as well as internally-guided eye movements allow us to flexibly explore the visual environment, their differential neural mechanisms remain elusive. A better understanding of these neural mechanisms will help us to understand the control of action and to elucidate the nature of cognitive deficits in certain psychiatric populations (e.g. schizophrenia) that show increased latencies in volitional but not visually-guided saccades. Both the superior precentral sulcus (sPCS) and the intraparietal sulcus (IPS) are implicated in the control of eye movements. However, it remains unknown what differential contributions the two areas make to the programming of visually-guided and internally-guided saccades. In this study we tested the hypotheses that sPCS and IPS distinctly encode internally-guided saccades and visually-guided saccades. We scanned subjects with fMRI while they generated visually-guided and internally-guided delayed saccades. We used multi-voxel pattern analysis to test whether patterns of cue related, preparatory and saccade related activation could be used to predict the direction of the planned eye movement. Results indicate that patterns in the human sPCS predicted internally-guided saccades but not visually-guided saccades in all trial periods and patterns in the IPS predicted internally-guided saccades and visually-guided saccades equally well. The results support the hypothesis that the human sPCS and IPS make distinct contributions to the control of volitional eye movements.     

Behavioral, but not reward, risk modulates activation of prefrontal, parietal, and insular cortices

Risky decisions may involve uncertainty about possible outcomes (i.e., reward risk) or uncertainty about which action should be taken (i.e., behavioral risk). Determining whether different forms of risk have distinct neural correlates is a central goal of neuroeconomic research. In two functional magnetic resonance imaging experiments, subjects viewed shapes that had well-learned response-reward contingencies. Magnitude of a monetary reward was held constant within one experiment, whereas expected value was held constant within the other. Response selection, in the absence of behavioral risk, evoked activation within a broad set of brain regions, as had been found in prior studies. However, behavioral risk additionally modulated activation in prefrontal, parietal, and insular regions, within which no effect of reward risk was observed. Reward delivery, in comparison with omission, evoked increased activity in the ventromedial prefrontal cortex and the nucleus accumbens. We conclude that distinct brain systems are recruited for the resolution of different forms of risk.     

Functional lateralization of the human premotor cortex during sequential movements

A neurological truism is that each side of the brain controls movements on the opposite side of the body. Yet some left hemisphere brain lesions cause bilateral impairment of complex motor function and/or ideomotor apraxia. We report that the left dorsal premotor cortex of normal right-handed people plays a fundamental role in sequential movement of both right and left hands. Subjects performed sequential finger movements during functional magnetic resonance imaging of the motor cortices. In right-handed subjects, the volume of activated dorsal premotor cortex showed a left hemispheric predominance during hand movements. We suggest that the observed left premotor dominance contributes to the lateralization found in lesion studies.     

Multimodal action representation in human left ventral premotor cortex

We used functional magnetic resonance imaging (fMRI) to investigate the neural systems responding to the sight and to the sound of an action. Subjects saw a video of paper tearing in silence (V), heard the sound of paper tearing (A), and saw and heard the action simultaneously (A + V). Compared to a non-action control stimulus, we found that hearing action sounds (A) activated the anterior inferior frontal gyrus and middle frontal gyrus in addition to primary auditory cortex. The anterior inferior frontal gyrus, which is known to be activated by environmental sounds, also seems to be involved in recognizing actions by sound. Consistent with previous research, seeing an action video (V) compared with seeing a non-action video activated the premotor cortex, intraparietal cortex, and the pars opercularis of the inferior frontal gyrus. An A + V facilitation effect was found in the ventral premotor cortex on the border of areas 44, 6, 3a, and 3b for the action stimuli but not for the control stimuli. This region may be involved in integrating multimodal information about actions. These data provide evidence that the ventral premotor cortex may provide an action representation that abstracts across both agency (self and other) and sensory modality (hearing and seeing). This function may be an important precursor of language functions.     

Some surprising findings on the involvement of the parietal lobe in human memory

The posterior parietal lobe is known to play some role in a far-flung list of mental processes: linking vision to action (saccadic eye movements, reaching, grasping), attending to visual space, numerical calculation, and mental rotation. Here, we review findings from humans and monkeys that illuminate an untraditional function of this region: memory. Our review draws on neuroimaging findings that have repeatedly identified parietal lobe activations associated with short-term or working memory and episodic memory. We also discuss recent neuropsychological findings showing that individuals with parietal lobe damage exhibit both working memory and long-term memory deficits. These deficits are not ubiquitous; they are only evident under certain retrieval demands. Our review elaborates on these findings and evaluates various theories about the mechanistic role of the posterior parietal lobe in memory. The available data point towards the conclusion that the posterior parietal lobe plays an important role in memory retrieval irrespective of elapsed time. However, the available data do not support simple dichotomies such as recall versus recognition, working versus long-term memory. We conclude by formalizing several open questions that are intended to encourage future research in this rapidly developing area of memory research.     

Sensory-motor and cognitive functions of the human posterior parietal cortex involved in manual actions

The posterior parietal cortex (PPC) is considered the dominant structure in the dorsal stream of visual processing, defined in the context of systems for perception and action. It is well-established that the human PPC is critical to sensory-motor transformations involved in online manual actions. A related body of literature identifies the PPC as important to cognitive aspects of action representation such as imagery, tool use, and gestures. The goal of the present paper is to review and compare the PPC contribution to representations of both motor control and motor cognition. Relating the sensory-motor and cognitive components of PPC function is important for an understanding of integrative representations of manual actions and the relation between perception, action, and cognition. Proposed theories of multiple dorsal stream systems supporting different action-relevant goals are discussed.     

Space and the parietal cortex

Current views of the parietal cortex have difficulty accommodating the human inferior parietal lobe (IPL) within a simple dorsal versus ventral stream dichotomy. In humans, lesions of the right IPL often lead to syndromes such as hemispatial neglect that are seemingly in accord with the proposal that this region has a crucial role in spatial processing. However, recent imaging and lesion studies have revealed that inferior parietal regions have non-spatial functions, such as in sustaining attention, detecting salient events embedded in a sequence of events and controlling attention over time. Here, we review these findings and show that spatial processes and the visual guidance of action are only part of the repertoire of parietal functions. Although sub-regions in the human superior parietal lobe and intraparietal sulcus contribute to vision-for-action and spatial functions, more inferior parietal regions have distinctly non-spatial attributes that are neither conventionally 'dorsal' nor conventionally 'ventral' in nature.     

The premotor theory of attention and the Simon effect

In the paper by Hommel (2011-this issue), the roles of the theory of event coding (TEC) and the premotor theory of attention (PMTA) for the Simon effect were considered. PMTA was treated by Hommel in terms of the proposal that attentional orienting can be viewed as the preparation of a saccade towards a certain location, and was dismissed as providing no useful contribution for an attentional explanation of the Simon effect. Here we considered a more recent and broader conception of the PMTA, compared this approach with TEC, and confronted both approaches with a few studies focusing on the role of spatial attention for the Simon effect. It was argued that PMTA may account more easily for various studies examining the influence of spatial attention on the Simon effect. We concluded our paper by listing some elements that an overall encompassing theory on the Simon effect should contain.     

Body image and the parietal lobes

In this review, the history of the concept of the body image in neuropsychiatry is presented. Links between the parietal cortex and the body image are discussed and the possible role of the parietal lobe in psychiatric disorders noted. The link between parietal lobe function and some neurophilosophical concepts are introduced.     

Gaze-dependent deviation in pointing induced by transcranial magnetic stimulation over the human posterior parietal cortex

Signals arising from the saccadic system influence the planning and generation of pointing movements, and the posterior parietal cortex (PPC) appears to play a vital role in that interaction. The authors demonstrate in the present study that during visual fixation, eye-position signals can dominate pointing responses when the activity in the PPC contralateral to the moving limb is disrupted with transcranial magnetic stimulation (TMS). In particular, when presented with targets in peripheral vision, participants (N=5) exposed to TMS over the PPC failed to show the normal pattern of responses in which pointing movements end up farther away from the goal target. Instead, they tended to point more toward the current point of visual fixation. Those results suggest that the PPC is involved in integrating eye-position and visual information to affect reaching in the contralateral arm.     

An area specifically devoted to tool use in human left inferior parietal lobule

A comparative fMRI study by Peeters et al. (2009) provided evidence that a specific sector of left inferior parietal lobule is devoted to tool use in humans, but not in monkeys. We propose that this area represents the neural substrate of the human capacity to understand tool use by using causal reasoning.     

Audiotactile multisensory interactions in human information processing

Abstract:  The last few years has seen a very rapid growth of interest in how signals from different sensory modalities are integrated in the brain to form the unified percepts that fill our daily lives. Research on multisensory interactions between vision, touch, and proprioception has revealed the existence of multisensory spatial representations that code the location of external events relative to our own bodies. In this review, we highlight recent converging evidence from both human and animal studies that has revealed that spatially-modulated multisensory interactions also occur between hearing and touch, especially in the space immediately surrounding the head. These spatial audiotactile interactions for stimuli presented close to the head can affect not only the spatial aspects of perception, but also various other non-spatial aspects of audiotactile information processing. Finally, we highlight some of the most important questions for future research in this area.     

Lateralized spatial and object memory encoding in entorhinal and perirhinal cortices

The perirhinal and entorhinal cortices are critical components of the medial temporal lobe (MTL) declarative memory system. Study of their specific functions using blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI), however, has suffered from severe magnetic susceptibility signal dropout resulting in poor temporal signal-to-noise (tSNR) and thus weak BOLD signal detectability. We have demonstrated that higher spatial resolution in the z-plane leads to improved BOLD fMRI signal quality in the anterior medial temporal lobes when using a 16-element surface coil array at 3 T (Tesla). Using this technique, the present study investigated the roles of the anterior medial temporal lobe, particularly the entorhinal and perirhinal cortices, in both object and spatial memory. Participants viewed a series of fractal images and were instructed to encode either the object's identity or location. Object and spatial recognition memory were tested after 18-sec delays. Both the perirhinal and entorhinal cortices were active during the object and spatial encoding tasks. In both regions, object encoding was biased to the left hemisphere, whereas spatial encoding was biased to the right. A similar hemispheric bias was evident for recognition memory. Recent animal studies suggest functional dissociations among regions of the entorhinal cortex for spatial vs. object processing. Our findings suggest that this process-specific distinction may be expressed in the human brain as a hemispheric division of labor.     

Anticipating action effects recruits audiovisual movement representations in the ventral premotor cortex

When table tennis players anticipate the course of the ball while preparing their motor responses, they not only observe their opponents striking the ball but also listen to events such as the sound of racket–ball contact. Because visual stimuli can be detected more easily when accompanied by a sound, we assumed that complementary sensory audiovisual information would influence the anticipation of biological motion, especially when the racket–ball contact is not presented visually, but has to be inferred from continuous movement kinematics and an abrupt sound. Twenty-six observers were examined with fMRI while watching point-light displays (PLDs) of an opposing table tennis player. Their task was to anticipate the resultant ball flight. The sound was presented complementary to the veracious event or at a deviant time point in its kinematics.Results showed that participants performed best in the complementary condition. Using a region-of-interest approach, fMRI data showed that complementary audiovisual stimulation elicited higher activation in the left temporo-occipital middle temporal gyrus (MTGto), the left primary motor cortex, and the right anterior intraparietal sulcus (aIPS). Both hemispheres also revealed higher activation in the ventral premotor cortex (vPMC) and the pars opercularis of the inferior frontal gyrus (BA 44). Ranking the behavioral effect of complementary versus conflicting audiovisual information over participants revealed an association between the complementary information and higher activation in the right vPMC. We conclude that the recruitment of movement representations in the auditory and visual modalities in the vPMC can be influenced by task-relevant cross-modal audiovisual interaction.