Neuroimaging of cerebral activations and deactivations associated with hypercapnia and hunger for air.

There are defined medullary, mesencephalic, hypothalamic, and thalamic functions in regulation of respiration, but knowledge of cortical control and the elements subserving the consciousness of breathlessness and air hunger is limited. In nine young adults, air hunger was produced acutely by CO(2) inhalation. Comparisons were made with inhalation of a N(2)/O(2) gas mixture with the same apparatus, and also with paced breathing, and with eyes closed rest. A network of activations in pons, midbrain (mesencephalic tegmentum, parabrachial nucleus, and periaqueductal gray), hypothalamus, limbic and paralimbic areas (amygdala and periamygdalar region) cingulate, parahippocampal and fusiform gyrus, and anterior insula were seen along with caudate nuclei and pulvinar activations. Strong deactivations were seen in dorsal cingulate, posterior cingulate, and prefrontal cortex. The striking response of limbic and paralimbic regions points to these structures having a singular role in the affective sequelae entrained by disturbance of basic respiratory control whereby a process of which we are normally unaware becomes a salient element of consciousness. These activations and deactivations include phylogenetically ancient areas of allocortex and transitional cortex that together with the amygdalar/periamygdalar region may subserve functions of emotional representation and regulation of breathing.

Brain activation in the processing of Chinese characters and words: a functional MRI study.

Functional magnetic resonance imaging was used to identify the neural correlates of Chinese character and word reading. The Chinese stimuli were presented visually, one at a time. Subjects covertly generated a word that was semantically related to each stimulus. Three sorts of Chinese items were used: single characters having precise meanings, single characters having vague meanings, and two-character Chinese words. The results indicated that reading Chinese is characterized by extensive activity of the neural systems, with strong left lateralization of frontal (BAs 9 and 47) and temporal (BA 37) cortices and right lateralization of visual systems (BAs 17-19), parietal lobe (BA 3), and cerebellum. The location of peak activation in the left frontal regions coincided nearly completely both for vague- and precise-meaning characters as well as for two-character words, without dissociation in laterality patterns. In addition, left frontal activations were modulated by the ease of semantic retrieval. The present results constitute a challenge to the deeply ingrained belief that activations in reading single characters are right lateralized, whereas activations in reading two-character words are left lateralized.

Reducing gist-based false recognition in older adults: encoding and retrieval manipulations.

Using a categorized pictures paradigm, Koutstaal and Schacter (1997) reported high levels of false recognition of lures that were categorically related to presented items. Although also shown by younger adults, false recognition was markedly higher for older adults. To probe the factors underlying this age difference, these experiments required participants to engage in more careful scrutiny of the items at retrieval or to notice specific differentiating perceptual features of the objects during encoding. False recognition was reduced with each of these manipulations, but neither manipulation, either separately or together, eliminated the age difference in false recognition. Older adults can considerably reduce false recognition if encouraged to use more stringent decision criteria. Persistent difficulty in opposing familiarity-based responding and comparatively more generic encoding may contribute to residual deficits.