The functional brain networks that underlie Early Stone Age tool manufacture

Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging tool for studying evoked hemodynamic changes within the brain. By this technique, changes in the optical absorption of light are recorded over time and are used to estimate the functionally evoked changes in cerebral oxyhemoglobin and deoxyhemoglobin concentrations that result from local cerebral vascular and oxygen metabolic effects during brain activity. Over the past three decades this technology has continued to grow, and today NIRS studies have found many niche applications in the fields of psychology, physiology, and cerebral pathology. The growing popularity of this technique is in part associated with a lower cost and increased portability of NIRS equipment when compared with other imaging modalities, such as functional magnetic resonance imaging and positron emission tomography. With this increasing number of applications, new techniques for the processing, analysis, and interpretation of NIRS data are continually being developed. We review some of the time-series and functional analysis techniques that are currently used in NIRS studies, we describe the practical implementation of various signal processing techniques for removing physiological, instrumental, and motion-artifact noise from optical data, and we discuss the unique aspects of NIRS analysis in comparison with other brain imaging modalities. These methods are described within the context of the MATLAB-based graphical user interface program, HomER, which we have developed and distributed to facilitate the processing of optical functional brain data.

The progress made in understanding the insula in the decade following an earlier review (Augustine, Neurol. Res., 7 (1985) 2-10) is examined in this review. In these ten years, connections have been described between the insula and the orbital cortex, frontal operculum, lateral premotor cortex, ventral granular cortex, and medial area 6 in the frontal lobe. Insular connections between the second somatosensory area and retroinsular area of the parietal lobe have been documented. The insula was found to connect with the temporal pole and the superior temporal sulcus of the temporal lobe. It has an abundance of local intrainsular connections and projections to subdivisions of the cingulate gyrus. The insula has connections with the lateral, lateral basal, central, cortical and medial amygdaloid nuclei. It also connects with nonamygdaloid areas such as the perirhinal cortex, entorhinal, and periamygdaloid cortex. The thalamic taste area, the parvicellular part of the ventral posteromedial nucleus, projects fibers to the ipsilateral insular-opercular cortex. In the past decade, confirmation has been given to the insula as a visceral sensory area, visceral motor area, motor association area, vestibular area, and language area. Recent studies have expanded the role of the insula as a somatosensory area, emphasizing its multifaceted, sensory role. The idea of the insula as limbic integration cortex has been affirmed and its role in Alzheimer's disease suggested.