Choice reaction tasks are performed faster when stimulus location corresponds to response location. This spatial stimulus–response compatibility effect affects performance at the level of action planning and execution. However, when response selection is completed before movement initiation, the Simon effect arises only at the planning level. The aim of this study was to ascertain whether when a precocious response selection is requested, the Simon effect can be detected on the kinematics characterizing the online control phase of a non-ballistic movement. Participants (...) were presented with red or green colored squares, which could appear on the right, left, above, or below a central cross. Depending on the square's color, participants had to release one of two buttons, then reach toward and press a corresponding lateral pad. We found evidence of the Simon effect on both action planning and on-line control. Moreover, the investigation of response conflict at the level of previous trials, a factor that might determine interference at the level of the current response, revealed a conflict adaptation process across trials. Results are discussed in terms of current theories concerned with the Simon effect and the distinction between action planning and control. (shrink)

The parietal cortex is divided into two major functional regions: the anterior parietal cortex that includes primary somatosensory cortex, and the posterior parietal cortex (PPC) that includes the rest of the parietal lobe. The PPC contains multiple representations of space. In Dijkerman & de Haan's (D&dH's) model, higher spatial representations are separate from PPC functions. This model should be developed further so that the functions of the somatosensory system are integrated with specific functions within the PPC and higher spatial representations. (...) Through this further specification of the model, one can make better predictions regarding functional interactions between somatosensory and visual systems. (shrink)

Dijkerman & de Haan (D&dH) propose a somatosensory perceptual pathway that informs a consciously accessible body image, and an action pathway that provides information to a body schema, which is not consciously accessible. We argue that the body schema may become accessible to consciousness in some circumstances, possibly resulting from cross talk, but that this may be detrimental to skilled movement production.

Evidence for a dichotomy between the planning of an action and its on-line control in humans is reviewed. This evidence suggests that planning and control each serve a specialized purpose utilizing distinct visual representations. Evidence from behavioral studies suggests that planning is influenced by a large array of visual and cognitive information, whereas control is influenced solely by the spatial characteristics of the target, including such things as its size, shape, orientation, and so forth. Evidence from brain imaging and neuropsychology (...) suggests that planning and control are subserved by separate visual centers in the posterior parietal lobes, each constituting part of a larger network for planning and control. Planning appears to rely on phylogenetically newer regions in the inferior parietal lobe, along with the frontal lobes and basal ganglia, whereas control appears to rely on older regions in the superior parietal lobe, along with the cerebellum. Key Words: action; apraxia; control; illusions; optic ataxia; PET; planning; reaching;. (shrink)

The target article fails to disentangle the functional description from the structural description of the two somatosensory streams. Additional evidence and thorough reconsideration of the evidence cited argue for a functional distinction between the how processing and the what processing of somatosensory information, while questioning the validity and usefulness of the equation of these two types of processing with structural streams. We propose going one step further: to investigate how the distinct functional streams are coordinated via attention.

The functions of the somatosensory system are multiple. We use tactile input to localize and experience the various qualities of touch, and proprioceptive information to determine the position of different parts of the body with respect to each other, which provides fundamental information for action. Further, tactile exploration of the characteristics of external objects can result in conscious perceptual experience and stimulus or object recognition. Neuroanatomical studies suggest parallel processing as well as serial processing within the cerebral somatosensory system that (...) reflect these separate functions, with one processing stream terminating in the posterior parietal cortex (PPC), and the other terminating in the insula. We suggest that, analogously to the organisation of the visual system, somatosensory processing for the guidance of action can be dissociated from the processing that leads to perception and memory. In addition, we find a second division between tactile information processing about external targets in service of object recognition and tactile information processing related to the body itself. We suggest the posterior parietal cortex subserves both perception and action, whereas the insula principally subserves perceptual recognition and learning. (shrink)

I aim to show that the content of our perceptual states depends counterfactually on the action we want to perform. Most philosophical and psychological theories of perception claim or at least assume the opposite: they conceive of perception as allpurpose: what we want to do does not influence what we see. I will argue that the content of one's perceptual state does vary as the action one is inclined to perform varies. To put it very simply, what we see does (...) indeed depend on what we want to do. After clarifying what counterfactual dependence means in my claim, I will give a two step argument. (a) one's visual attention (sometimes) depends counterfactually on one's intention to perform an action (everything else being equal) and (b) one's perceptual content (always) depends counterfactually on one's visual attention (everything else being equal). If we put these claims together, what we get is that one's perceptual content depends counterfactually on one's intention to perform an action (everything else being equal). (shrink)

To study conscious experience we must, to some extent, trust introspective reports; yet introspective reports often do not merit our trust. A century ago, E.B. Titchener advocated extensive introspective training as a means of resolving this difficulty. He describes many of his training techniques in his four-volume laboratory manual of 1901- 1905. This paper explores Titchener's laboratory manual with an eye to general questions about the prospects of introspective training for contemporary consciousness studies, with a focus on the following examples: (...) introspective knowledge of the combination tones that arise when a musical interval is played; the 'flight of colours' in the afterimage of a field of bright, broad- spectrum light; and the possibility of non-obvious visual illusions. Introspective training appears to have some merit, but also to involve significant hazards. (shrink)