Lateralized suppression of dichotically presented digits after commissural section in man

Right-handed patients with surgical disconnection of the cerebral hemispheres cannot report verbal input to the left ear if diferent verbal stimuli have been channeled simultaneously to the right ear. With monaural stimulation, they show equal accuracy of report for the two ears. These findings highlight the dominance of the contralateral over the ipsilateral auditory projection system. Suppression of right-ear input is obtained in nonverbal tests. Dissociation between verbal and left-hand stereognostic responses indicate a right-left dichotomy for auditory experience in the disconnected hemispheres.     

Differential cerebral processing of noise and verbal stimuli

Psychophysiological measurements have indicated that the right cerebral hemisphere processes noises and other nonverbal data and that the left cerebral hemisphere processes verbal material. Direct physiological measurements, as expressed in summated auditory evoked cortical responses, unequivocally demonstrate that click noises show a greater amplitude of initial output over the right brain, and that verbal stimuli produce either equal or higher amplitudes of output over the left cerebral hemisphere.     

Hearing with the third ear: dichotic perception of a melody without monaural familiarity cues

Julesz has shown that cross-correlations between two patterns that appear random to either eye alone can give rise to the perception of form and depth when viewed stereoscopically. We produced auditory analogs by presenting eight simultaneous and continuous sine waves to both ears and by either phaseshifting or frequency-shifting one of them relative to its counterpart in the opposite ear. Particular tones were shifted in sequence such that a melody was heard which was undetectable by either ear alone.     

Cerebral dominance in musicians and nonmusicians

Musically experienced listeners recognize simple melodies better in the right ear than the left, while the reverse is true for naive listeners. Hence, contrary to previous reports, music perception supports the hypothesis that the left hemisphere is dominant for analytic processing and the right hemisphere for holistic processing.     

Unit activity: motiviation-dependent responses from midbrain neurons

Single neurons in the midbrain tegmentum of rats showed clear discriminatory responses to three tones announcing either food or water or no reinforcement. Subjects were required to press a single lever and remain motionless for 2 seconds during which time unit activity from several brain sites was recorded. One of the tones, randomly designated, was sounded halfway through this period. Manipulation of drive states revealed that the highest activity was associated with tones announcing the reinforcement for which the animal was most strongly motivated. Thus, from a hungry animal sustained or increased firing rates were elicited by a " food" tone and differentially lowered rates by the other tones.     

The medial frontal cortex and the rapid processing of monetary gains and losses

We report the observation of neural processing that occurs within 265 milliseconds after outcome stimuli that inform human participants about gains and losses in a gambling task. A negative-polarity event-related brain potential, probably generated by a medial-frontal region in or near the anterior cingulate cortex, was greater in amplitude when a participant's choice between two alternatives resulted in a loss than when it resulted in a gain. The sensitivity to losses was not simply a reflection of detecting an error; gains did not elicit the medial-frontal activity when the alternative choice would have yielded a greater gain, and losses elicited the activity even when the alternative choice would have yielded a greater loss. Choices made after losses were riskier and were associated with greater loss-related activity than choices made after gains. It follows that medial-frontal computations may contribute to mental states that participate in higher level decisions, including economic choices.     

Pitch memory: an advantage for the left-handed

In an auditory or musical task, subjects made pitch recognition judgments when the tones to be compared were separated by a sequence of interpolated tones. The left-handed subjects performed significantly better than the right-handed and also had a significantly higher variance. Further analysis showed that the superior performance was attributable largely to the left-handed subjects with mixed hand preference.     

Visual temporal order: a new illusion

Brief visutal stimuli presented in rapid sequience, one to the left and one to the right, appear to occur left first, then right, regardless of the actual order of presentation. This illutsion persists under conditions of forced-choice testing and does not vary with presemitation to the same or opposite retinal hemifields, A series of experiments suggests that this illutsion may be the product of an internal mechanism that scans visual inputs in a left-to-right order.     

Unilateral Increase of Auditory Sensitivity following Early Auditory Exposure

A 30-second exposure (priming) to a loud noise induced a long-lasting susceptibility to audiogenic seizures and a 15-decibel decrease in threshold to the Preyer acoustic startle reflex in C57BL/6J mice. Both effects were absent when the subjects were primed in one ear and subsequently tested in the contralateral ear. It was postulated that the primary effect of priming is an increase in auditory sensitivity due to changes in the ear itself or in those parts of the auditory system which receive their input exclusively from one ear.     

Neuroscience. More to seeing than meets the eye

A single event may elicit several different sensory stimuli such as vision, sound, and touch. But how does the brain know which of the many different stimuli arriving in the sensory cortex of the brain are connected? In her Perspective, de Gelder discusses new findings showing that when a touch is applied on the same side of the body as a visual cue, vision is enhanced (Macaluso et al.). She explains that this effect is due to neurons projecting from the somatosensory (touch) area of the sensory cortex back to the visual cortex. These neurons keep the visual cortex informed about tactile stimuli elicited at the same time as the visual stimuli.     

基于fNIRS的符号和非符号数量加工的脑机制研究

为探讨符号和非符号数量加工的特异性和非特异性问题以及二者间相互转换的神经机制,利用功能性近红外光谱成像技术(fNIRS)对30名成人进行测量,实验中让被试完成数量适应范式任务,结果发现:(1)非符号数量加工主要激活脑区为右顶上叶、右额上回和左右额中回,而符号数量加工则主要在左额中回有显著激活,且只有符号数量加工中出现了距离效应;(2)非符号向符号数量转换由左右顶上叶、左额上回和左右额中回负责,而符号向非符号数量转换则是由左顶上叶和左右额上回负责.研究结果既支持了符号和非符号数量加工的特异性观点,又进一步揭示符号和非符号数量相互转换有着不同的神经机制.     

Complementary hemispheric specialization in monkeys

Twenty-five split-brain monkeys were taught to discriminate two types of visual stimuli that engage lateralized cerebral processing in human subjects. Differential lateralization for the two kinds of discriminations was found; the left hemisphere was better at distinguishing between tilted lines and the right hemisphere was better at discriminating faces. These results indicate that lateralization of cognitive processing appeared in primates independently of language or handedness. In addition, cerebral lateralization in monkeys may provide an appropriate model for studying the biological basis of hemispheric specialization.     

Vision guides the adjustment of auditory localization in young barn owls

Barn owls raised with one ear plugged make systematic errors in auditory localization when the earplug is removed. Young owls correct their localization errors within a few weeks. However, such animals did not correct their auditory localization errors when deprived of vision. Moreover, when prisms were mounted in front of their eyes, they adjusted their auditory localization to match the visual error induced by the prisms, as long as the visual and auditory errors were within the same quadrant of directions. The results demonstrate that, during development, the visual system provides the spatial reference for fine-tuning auditory localization.     

Paradoxical effects after microinjection of morphine in the periaqueductal gray matter in the rat

Paradoxical, concurrent hyper-and hyporeactivity of a profound nature to specific stimuli occurred when 10 micrograms of morphine was microinjected bilaterally into the periaqueductal gray matter of the rat brain. Both effects at this site were dose-dependent. The hyperreactivity (to previously neutral auditory and visual stimuli) was obtained only with intracerebrally injected morphine and never with intraperitoneally injected morphine or with other opiates administered either way. Rapid tolerance to toxic doses of morphine developed at this site, as well as cross tolerance of the hyporeactivity to painful stimuli between routes (intracerebral to intraperitoneal) of morphine administration. Both the hyper- and hyporeactivity were fully reversible by intracerebral injection of naloxone in the periaqueductal gray. Thus, the periaqueductal gray appears to be a major pathway for morphine action.     

Functional specialization in rhesus monkey auditory cortex

Neurons in the lateral belt areas of rhesus monkey auditory cortex prefer complex sounds to pure tones, but functional specializations of these multiple maps in the superior temporal region have not been determined. We tested the specificity of neurons in the lateral belt with species-specific communication calls presented at different azimuth positions. We found that neurons in the anterior belt are more selective for the type of call, whereas neurons in the caudal belt consistently show the greatest spatial selectivity. These results suggest that cortical processing of auditory spatial and pattern information is performed in specialized streams rather than one homogeneously distributed system.     

Neuroscience. Regional differences in cortical organization

Although there are elegants maps of the human brain that reveal differences in cellular architecture between different cortical regions, there is not much information about how corresponding cortical regions differ between the left and right hemispheres. As Gazzaniga explains in his Perspective, new results reveal the surprising finding of asymmetry in area 22 (which is important for language processing) of the left and right hemisphere (Galuske et al.). Clusters of neurons in area 22 of the left hemisphere are spaced farther apart and have longer axons cabling them together than neuronal clusters in area 22 of the right hemisphere.     

Interhemispheric asymmetries of the modular structure in human temporal cortex

Language-relevant processing of auditory signals is lateralized and involves the posterior part of Brodmann area 22. We found that the functional lateralization in this area was accompanied by interhemispheric differences in the organization of the intrinsic microcircuitry. Neuronal tract tracing revealed a modular network of long-range intrinsic connections linking regularly spaced clusters of neurons. Although the cluster diameter was similar in both hemispheres, their spacing was about 20 percent larger in the left hemisphere. Assuming similar relations between functional and anatomical architecture as in visual cortex, the present data suggest that more functionally distinct columnar systems are included per surface unit in the left than in the right area 22.     

Temperature effects on the peripheral auditory apparatus

Cooling with a thermoelectric cold probe, well localized in the region of the cochlea, produces a rapid, reversible decrease in the amplitude and increase in the latency of the action potential induced by clicks. These changes closely resemble those produced by reducing click intensity. Temperature also affects the amplitude of the cochlear microphonic, but the amount of change is considerably less than, and is poorly correlated with, the amplitlude change of the action potential. It is speculated that temperature may act on a hypothetical " excitatory process" in the cochlea, which comes after the cochlear microphonic in the sequence leading to production of the action potential of the auditory nerve.     

Temporal lobe lesions and perception of species-specific vocalizations by macaques

Japanese macaques were trained to discriminate two forms of their coo vocalization before and after unilateral and bilateral ablation of the temporal cortex. Unilateral ablation of the left superior temporal gyrus, including auditory cortex, resulted in an initial impairment in the discrimination, but similar unilateral ablation of the right superior temporal gyrus had no effect. Bilateral temporal lesions including auditory cortex completely abolished the ability of the animals to discriminate their coos. Neither unilateral nor bilateral ablation of cortex dorsal to and sparing the auditory cortex had any effect on the discrimination. The perception of species-specific vocalizations by Japanese macaques seems to be mediated by the temporal cortex, with the left hemisphere playing a predominant role.     

Auditory information from subcortical electrical stimulation in cats

Animals trained to respond to sound stimuli were found to perform the learned response when they were electrically stimulated through electrodes chronically implanted in subcortical structures of the auditory pathway. Other animals trained to respond to electrical stimulation of subcortical auditory structures showed differential transfer effects depending on the positions of the stimulating electrodes.