The linkage between stimulus frequency and covert peak areas as it relates to monaural localization

Head-related transfer functions for differently centered narrow noise bands were obtained on 6 subjects. Derived from these measurements were covert peak areas (CPAs), defined as the spatial constellation of loudspeakers that generates maximal sound pressure at the entrance of the ear canal for specific bands of frequency. On the basis of previous data, we proposed that different frequency bands served as important spectral cues for monaural localization of sounds from different loci and that location judgments were directed toward the CPAs associated with the different bands. In the first study, the stimuli were bandpass filtered so that they contained only those frequencies whose associated CPAs occupied either the monaural listener’s “upper” or “lower” spatial regions. Loudspeakers, separated by 15°, were stationed in the left hemifield, ranging from 0° to 180° azimuth and ?45° to 60° elevation. Subjects reported the loudspeaker from which the sound appeared to originate. Judgments of the sound’s elevation were in general accord with the CPAs associated with the different frequency segments. In the second study, monaural localization tests were administered in which different 2.0-kHz-wide frequency bands linked with specific CPAs were notch filtered from a 3.5-kHz highpass noise band. For the control condition, the highpass noise was unfiltered. The data demonstrated that filtering a frequency segment linked with specific CPAs resulted in significantly fewer location responses directed toward that particular spatial region. These results demonstrate in greater detail the relation between the directional filtering properties of the pinna and monaural localization of sound.     

Perioral somatosensory determinants of nursing behavior in Norway rats (Rattus norvegicus)

Prior to assuming the upright crouching posture over their pups during nursing bouts, lactating rats typically engage in several oral behaviors, including nuzzling, licking and rearranging pups. By acutely depriving dams of various aspects of perioral stimulation from pups (with anesthesia of the mystacial pads or of the tongue, with mouth suturing, or with muzzling), we found the following: (1) Distal stimulation from pups maintains proximity-seeking behavior, but is insufficient to stimulate nursing behavior. (2) Lack of tongue feedback decreases pup licking and hastens the onset of crouching. (3) Snout, but not tongue, contact with pups is required for hovering over them. (4) The position of the dam while hovering over her litter enables the pups to gain access to her ventrum, thereby provoking her upright, crouching posture. (5) Older pups are capable of bypassing the dam's perioral attentions and stimulating crouching directly by burrowing under the dam's ventrum.     

The role of propulsive muscles of the shoulder during quadrupedalism in vervet monkeys (Cercopithecus aethiops): implications for neural control of locomotion in primates

In comparative anatomical studies of the shoulder, the humeral retractors are often grouped together as propulsive muscles, which are important in the propulsive stroke of the forelimb during quadrupedal locomotion. Electromyographic (EMG) analyses of these muscles in opossums, cats, and dogs in general have confirmed such conclusions. An EMG study of chimpanzee shoulder muscles during knuckle-walking found, however, that the humeral retractors are either inactive or perform a function unrelated to propulsion (Larson & Stern, 1987). This contrast in muscle recruitment patterns between chimpanzees and more "typical" mammalian quadrupeds was attributed to the derived morphology of the chimpanzee shoulder. The present study examines the activity patterns of the humeral retractors in the vervet monkey, a primate more closely resembling nonprimate mammals in its shoulder morphology. The results of this EMG analysis show that despite the significant differences in anatomy between chimpanzees and vervets, the two species display very similar muscle recruitment patterns during quadrupedalism, and there is evidence for this same pattern in other species of primates. These differences in muscle activity patterns between primates and nonprimate mammals may be related to changes in the neurological control of locomotion in primates due to the evolutionary development of manipulative abilities in the primate forelimb.     

Regional cerebral glucose metabolism in aphemia: A case report

Local cerebral metabolism was determined in a patient suffering aphemia following cerebral infarction using the 18FDG-PET technique. The syndrome was characterized by profound ictal nonfluency with sparing of other language functions. Speech subsequently improved so that content and grammar were appropriate but mild dysprosody persisted. Conventional CT showed no lesion of the left hemisphere while PET revealed a discrete focus of hypometabolism on the left which partially resolved on serial studies. The metabolic lesion could be localized to the region of the inferior precentral gyrus and the adjacent subcortical space.     

The culture of perceptual expertise and the other-race effect

In our commentary, we propose that the ORE can be viewed as a form of perceptual expertise. Like experts, we recognize own-race faces at the subordinate level as individuals and novices when recognize other-race faces at the basic level of race. Applying a perceptual expertise account, we explain the ORE in terms of its cognitive, neural, and motivational factors. We suggest that by creating a culture of “other-race” expertise, improvements in other-race face recognition can be achieved.     

Semantic emphasis in causal sentences

A shift in emphasis can change the truth-value of a singular causal sentence. This poses a challenge to the view that singular sentences predicate a relation. I argue that emphasized causal sentences conjoin predication of a causal relation between events with predication of a relation of causal relevance between states of affairs (or perhaps facts). This is superior to the treatments of such sentences offered by Achinstein, Dretske, Kim, Sanford, Bennett, and Levin. My proposal affords clarity regarding logical structure, at least at a certain level of detail. It makes the relation between the content of an emphasized causal sentence and the unemphasized version clear. It answers some questions about the ontological requirements of the truth of emphasized causal sentences, without introducing new entities (as do some other accounts) or unacceptable consequences for identity and individuation of events.     

Maternal aggression: disruption by perioral anesthesia in lactating Long-Evans rats (Rattus norvegicus)

Role of perioral somatosensation in the display of maternal aggression in Long-Evans Norway rats (Rattus norvegicus) was investigated during early lactation by local anesthesia of the mystacial pads with lidocaine, which blocks conduction in the infraorbital nerve. Acute perioral anesthesia markedly reduced the likelihood that maternal aggression was expressed; this effect of perioral anesthesia was not ameliorated by a repeated test with the same treatment or by pretreatment fighting experience. The dams that fought with the intruder during perioral anesthesia did so after greatly increased sniffing contact and with decreased vigor compared with controls. Males that were attacked tended to freeze, whereas males that were not attacked were active. Thus, trigeminal afferents are critical for the initiation and normal execution of maternal aggression responses in Norway rats.