Brodmann's cytoarchitectonic map of the human cortex designates area 4 as cortex in the anterior bank of the precentral sulcus and area 6 as cortex encompassing the precentral gyrus and the posterior portion of the superior frontal gyrus on both the lateral and medial surfaces of the brain. More than 70 years ago, Fulton proposed a functional distinction between these two areas, coining the terms primary motor areafor cortex in Brodmann area 4 and premotor areafor cortex in Brodmann area 6. The parcellation of the cortical motor system has subsequently become more complex. Several nonprimary motor areas have been identified in the brain of the macaque monkey, and associations between anatomy and function in the human brain are being tested continuously using brain mapping techniques. In the present review, the authors discuss the unique properties of the primary motor area (M1), the dorsal portion of the premotor cortex (PMd), and the ventral portion of the premotor cortex (PMv). They end this review by discussing how the premotor areas influence M1.

Our study uses the combined transcranial magnetic stimulation/positron emission tomography (TMS/PET) method for elucidating neural connectivity of the human motor system. We first altered motor excitability by applying low-frequency repetitive TMS over two cortical motor regions in separate experiments: the dorsal premotor and primary motor cortices. We then assessed the consequences of modulating motor excitability by applying single-pulse TMS over the primary motor cortex and measuring: 1) muscle responses with electromyography and 2) cerebral blood flow with PET. Low-frequency repetitive stimulation reduced muscle responses to a similar degree in both experiments. To map networks of brain regions in which activity changes reflected modulation of motor excitability, we generated t-statistical maps of correlations between reductions in muscle response and differences in cerebral blood flow. Low-frequency repetitive stimulation altered neural activity differently in both experiments. Neural modulation occurred in multiple brain regions after dorsal premotor cortex stimulation; these included motor regions in the frontal cortex as well as more associational regions in the parietal and prefrontal cortices. In contrast, neural modulation occurred in a smaller number of brain regions after primary motor cortex stimulation, many of these confined to the motor system. These findings are consistent with the known differences between the dorsal premotor and primary motor cortices in the extent of cortico-cortical anatomical connectivity in the monkey.

The broader autism phenotype (BAP) is a term applied to individuals with personality and cognitive traits that are similar to but milder than those observed in autism spectrum disorder (ASD). Subtle autistic traits in the core diagnostic domains of social communication and rigid behavior were described in family members of people with an ASD even in the initial reports of ASD. In this article, we discuss the benefits and limitations of researching the BAP in typically developing individuals for understanding autism and development.

Specific abnormalities of vision in schizophrenia have been observed to affect high-level and some low-level integration mechanisms, suggesting that people

Size constancy is the result of cognitive scaling operations that enable us to perceive an object as having the same size when presented at different viewing distances. In this article, we review the literature on size and distance perception to form an overarching synthesis of how the brain might combine retinal images and distance cues of retinal and extra-retinal origin to produce a perceptual visual experience of a world where objects have a constant size. A convergence of evidence from visual psychophysics, neurophysiology, neuropsychology, electrophysiology and neuroimaging highlight the primary visual cortex (V1) as an important node in mediating size–distance scaling. It is now evident that this brain area is involved in the integration of multiple signals for the purposes of size perception and does much more than fulfil the role of an entry position in a series of hierarchical cortical events. We also discuss how information from other sensory modalities can also contribute to size–distance scaling and shape our perceptual visual experience.