We used psychophysical and functional MRI (fMRI) adaptation to examine how and where the visual configural cues underlying identification of facial ethnicity, gender, and identity are processed. We found that the cortical regions showing selectivity to these cues are distributed widely across the inferior occipital cortex, fusiform areas, and the cingulate gyrus. These regions were not colocalized with areas activated by traditional face area localizer scans. Traditional face area localizer scans isolate regions defined by stronger fMRI responses to a random series of face images than to a series of non-face images. Because these scans present a random assortment of face images, they presumably produce the strongest responses within regions containing neurons that are face-sensitive but not highly tuned for face type. These areas might be expected to show only weak selective adaptation effects. In contrast, the largest responses to our selective adaptation paradigm would be expected within areas containing more selectively tuned neurons that might be expected to show only a sparse collective response to a series of random faces. Many aspects of face processing (e.g., prosopagnosia, recognition, and configural vs. featural processing) are likely to rely heavily on regions containing high proportions of neurons that show selective tuning for faces.

Three studies of normal human newborns and of newborns of methadone-maintained mothers evaluated how orotactile (pacifier) and orogustatory (sucrose) stimulation, alone and in combination, affected crying behavior, heart rate, gross motor activity, eye opening, and hand-mouth coordination. For each measure of infant state, pacifier and sucrose stimulation each caused significant changes that followed very different time courses. Orotactile (pacifier) stimulation precipitated immediate changes in all behaviors, and, when the pacifier was removed, all behaviors soon reverted to baseline levels. The changes precipitated by orogustatory (sucrose) stimulation were more gradual but extended well beyond the end of sucrose administration. Although both pacifier and sucrose influences are mediated orally as opposed to in the stomach or intestine, the effects involve different brain pathways. The fact that infants born to methadone-maintained mothers did not change their behaviors during or after sucrose administration but that their reactions to pacifier stimulation could not be distinguished from those of normal infants suggests that reactions to sucrose are mediated centrally by endogenous opioids while those to the pacifier work through other central mechanisms. These findings with human newborns are consonant with those of many animal studies that have also shown rapid onset and rapid offset for contact- and suckling-induced behavioral changes, slower onset and slower offset for changes induced by taste, and opioid mediation of changes induced by the taste of sucrose. Orogustatory and orotactile influences on affect, action, and cardiovascular function are discussed from the perspectives of energetics and growth, central determinants of state, motivation, and learning during the newborn period.

Phenylketonuria (PKU) is a genetic disorder in which the hydroxylation of phenylalanine (Phe) to tyrosine is severely disrupted. If PKU is left untreated, severe mental retardation results. The accepted treatment is to restrict dietary intake of Phe. It has generally been thought that cognitive impairments are prevented if levels of Phe in plasma are maintained at or below five times the normal level. However, we recently documented that children treated early and continuously for PKU or children mildly hyperphenylalaninemic, who have levels of Phe in plasma approximately three to five times normal, still have cognitive impairments. These impairments are specific to the functions of frontal cortex (A. Diamond, W. Hurwitz, E. Lee, W. Grover, and C. Minarcik, unpublished observations). To investigate the mechanism underlying these cognitive deficits, an animal model of this condition was developed and characterized. Thirty-six rat pups were divided into three groups. The first group was treated pre- and postnatally with Phe and alpha-methylphenylalanine (a phenylalanine hydroxylase inhibitor). The second group was injected postnatally with Phe and alpha- methylphenylalanine. The third group received postnatal control injections. The mild plasma Phe elevations in the two experimental groups produced significant behavioral and neurochemical effects. Both experimental groups were impaired on a task dependent on frontal cortex, delayed alternation. Levels of dopamine, homovanillic acid (HVA), norepinephrine, and 5-hydroxyindole acetic acid (5-HIAA) were measured in medial prefrontal cortex, anterior cingulate cortex, striatum, and nucleus accumbens. The largest neurochemical reductions observed were in HVA and were in the two frontal cortical areas (medial prefrontal cortex and anterior cingulate cortex). There were modest reductions in HVA in the nucleus accumbens but no significant changes in HVA, or in any other metabolite or neurotransmitter, in the striatum. The levels of 5-HIAA were also reduced in all brain regions examined. There was no effect on norepinephrine in any of the four regions examined. Reduced levels of HVA in medial prefrontal cortex were the only neurochemical effect that significantly correlated with every measure of performance on the delayed alternation task. This study provides evidence of deleterious effects from mild elevations in the levels of Phe in plasma previously considered small enough to be safe. These effects include impaired performance on a cognitive task dependent on frontal cortex and reduced HVA levels in frontal cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Previous studies have shown that attention to a particular stimulus feature, such as direction of motion or color, enhances neuronal responses to unattended stimuli sharing that feature. We studied this effect psychophysically by measuring the strength of the motion aftereffect (MAE) induced by an unattended stimulus when attention was directed to one of two overlapping fields of moving dots in a different spatial location. When attention was directed to the same direction of motion as the unattended stimulus, the unattended stimulus induced a stronger MAE than when attention was directed to the opposite direction. Also, when the unattended location contained either uncorrelated motion or had no stimulus at all an MAE was induced in the opposite direction to the attended direction of motion. The strength of the MAE was similar regardless of whether subjects attended to the speed or luminance of the attended dots. These results provide further support for a global feature-based mechanism of attention, and show that the effect spreads across all features of an attended object, and to all locations of visual space.