Right hemisphere superiority for subitising

Lateral differences in the enumeration of small sets of items (i.e., between two and five) were investigated in a normal adult sample. Confounds due to stimulus repetition, which have characterised previous subitising research, were eliminated in a task involving the presentation of purely random item arrays to the left and right visual fields. The results indicated a clear left visual field advantage for the enumeration of arrays containing three to four items. This finding is consistent with the widely held view that the subitising process is used to enumerate arrays of up to four items, and calls into question Butterworth's (1999) recent claim that subitising is a left hemisphere process. The implications for previous pattern recognition and visual process accounts of this ability are considered.     

Right hemisphere superiority for subitising

Lateral differences in the enumeration of small sets of items (i.e., between two and five) were investigated in a normal adult sample. Confounds due to stimulus repetition, which have characterised previous subitising research, were eliminated in a task involving the presentation of purely random item arrays to the left and right visual fields. The results indicated a clear left visual field advantage for the enumeration of arrays containing three to four items. This finding is consistent with the widely held view that the subitising process is used to enumerate arrays of up to four items, and calls into question Butterworth's (1999) recent claim that subitising is a left hemisphere process. The implications for previous pattern recognition and visual process accounts of this ability are considered.     

Right hemisphere superiority for initial stages of letter processing

When single letters, which could be perfectly recognized when presented alone, were embedded in an overlapping masking stimulus, observers recognized more letters from the left than from the right visual field. This left visual field-right hemisphere advantage persisted over short time intervals between the letter and the mask, regardless of which stimulus occurred first. Such results suggest that the right cerebral hemisphere is more efficient than the left at extracting relevant visual features of letters when the letters are perceptually degraded, even though letters are highly associated with language and, therefore, readily processed along verbal-analytic dimensions.     

Right hemisphere advantage for evaluating emotional facial expressions

The ability to evaluate the intensity of emotional facial expressions was investigated in patients undergoing the intracarotid sodium amytal procedure. It was found that when the hemisphere non-dominant for language (usually right) was anesthetized, the patients' ratings of the intensity of emotional expressions in photographs were lower than baseline ratings of these expressions. Such an effect was not seen with anesthetization of the hemisphere dominant for language (usually left). Ratings of shades of gray (which served as control stimuli) showed no such effect. The findings are interpreted in terms of a right hemisphere superiority in the perception and evaluation of emotional expression.     

Right hemisphere superiority for programming oculomotion: evidence from simple reaction time experiments

Simple reaction times (RTs) to lateralized unstructured visual stimuli were measured in normal subjects while they were carrying out concomitant oculomotor tasks. Four tasks were used. In the first task, subjects had to find the correct path in a maze presented at the centre of a screen; in the second task, subjects had to follow a bright dot moved on a screen with variable direction, trajectory and velocity with their eyes; in the third task, the subjects had to follow a bright dot moved back and forth either horizontally or vertically along the same trajectory and at a constant velocity; in the fourth task, the subjects had to monitor the movement of a bright dot moved with variable direction, trajectory and velocity without moving the eyes. In all tasks, with the exception of the third, there was a selective lengthening of RTs mediated by the right hemisphere. It is concluded that the right hemisphere is dominant in programming eye movements.     

Left hemisphere superiority for visuospatial functions in left-handers

Male and female left- and right-handers have been tested with a divided visual field technique on a visuospatial (discrimination of angle width) and on a verbal task (vowel-consonant discrimination) using either a choice or a Go-No-go manual reaction time paradigm. Right-handers showed the expected pattern of hemispheric asymmetries with an advantage of the right hemisphere in the visuospatial task and an advantage of the left hemisphere in the verbal task. Such effects were statistically reliable only in male subjects. Left-handers, on the contrary, showed a different pattern of asymmetries. In the visuospatial task there was an overall superiority of the left hemisphere, while no hemispheric asymmetry was found in the verbal task.     

Right hemisphere dominance for praxis and left hemisphere dominance for speech in a left-hander

A left-handed woman suffered marked apraxia and agraphia in the non-dominant hand, without aphasia, following a large right hemisphere infarct. This is a case of co-dominance with reading and speech mediated by the intact left hemisphere and praxis by the damaged right hemisphere     

Right hemisphere writing and spelling

Abstract

The role of the right hemisphere in language processing has been extensively researched over the past 30 years. The focus of this work has been on written word comprehension, spoken word comprehension and spoken word production, with less attention paid to written word production. Despite this, there is mounting evidence that the isolated right hemisphere is capable of written language production. The aim of this paper is to review this evidence. The most pertinent data come from split-brain patients, patients with extensive left hemisphere lesions and patients who have undergone left hemispherectomy. The data show the isolated right hemisphere of split-brain patients is capable of written language even if spoken word production is absent. The right hemisphere can also develop a capacity to write and spell after damage to the left hemisphere. Further, the type of spelling skill displayed by the right hemisphere is constrained to a lexico-semantic strategy. As with studies of right hemisphere written word comprehension, significant problems exist when interpreting writing and spelling behaviour, and there are unique problems associated with assessment of writing and spelling data in patient groups. These problems are discussed, and suggestions for further investigations of right hemisphere written word production are made.     

Right hemisphere sensitivity to feedback

The present studies sought to determine whether feedback-related emotional states influence perceptual and/or response processes within the right hemisphere. The task involved the presentation of a positive, neutral or negative feedback signal followed by a target in the left (LVF) or right (RVF) visual field which was spatially compatible or incompatible with its assigned response. The first two studies demonstrated that when a LVF target required a left-hand response, RTs were delayed following negative feedback and facilitated following positive feedback. These effects occured when the target followed the feedback signal by either 100 or 500 msec, and were evident when the response selection was based on either the target's spatial location or its form. Experiment 3 showed that these feedback effects disappeared when verbal information conveyed the appropriate response. These findings indicate that feedback-related emotional processes modulate sensory- response translation processes within the right hemisphere.     

Right hemisphere patients''judgements on emotions

A triadic comparison technique was used to assess brain-damaged patients' ability to judge the relatedness of a number of emotions, using either a pictorial or verbal material. Emotionally neutral material served as a control. Right hemisphere patients also differed from normals in processing emotions when presented with verbal material. It is suggested that central rather than only peripheral aspects in recognition of emotions are disturbed after injury to the right hemisphere.     

The nature of the sex difference in right hemisphere superiority for face recognition

Two experiments on right hemisphere superiority for upright face recognition by normal adults are reported. Experiment 1 showed that right hemisphere superiority for face recognition is affected by the ratio of stimuli to trials used in the experiment. A low ratio of stimuli to trials (Condition A) gave right hemisphere superiorities for both male and female subjects, whereas a high ratio of stimuli to trials (Condition C) led to no visual hemifield difference for male or for female subjects. The use of a stimuli to trials ratio intermediate between those of Condition A and Condition C resulted in a sex difference, with males but not females showing right hemisphere superiority in Condition B. It is argued that both males and females possess asymmetrically organised face processing mechanisms whose operation is dependent upon the level of difficulty of the face memory task used in a particular experiment, but that there is a sex difference in the range across which these mechanisms can operate. Experiment 2 demonstrated that this sex difference does not simply reflect an underlying sex difference in the tendency to use configurational or piecemeal strategies in such experiments.     

Eye-catching: Right hemisphere attentional bias for emotional pictures

To examine whether healthy individuals spontaneously direct attention to emotional pictures, eye movements were monitored continuously during the presentation of pairs of emotional and neutral pictures. A right hemisphere advantage was expected for initial orienting to emotional pictures. When an emotionally arousing picture was presented in the left visual hemifield, i.e., to the right hemisphere, the initial saccade was more often issued towards it, irrespective of valence. Negative pictures did not lead to avoidance throughout the 8-second trials; rather, both positive and negative valence held attention. This study adds to the evidence that overt attention to visual stimuli is boosted by emotion and that there is a right hemisphere advantage for orienting to emotional cues.     

Representations of facial identity in the left hemisphere require right hemisphere processing

A quintessential example of hemispheric specialization in the human brain is that the right hemisphere is specialized for face perception. However, because the visual system is organized contralaterally, what happens when faces appear in the right visual field and are projected to the nonspecialized left hemisphere? We used divided field presentation and fMRI adaptation to test the hypothesis that the left hemisphere can recognize faces, but only with support from the right hemisphere. Consistent with this hypothesis, facial identity adaptation was observed in the left fusiform face area when a face had previously been processed by the right hemisphere, but not when it had only been processed by the left hemisphere. These results imply that facial identity information is transferred from the right hemisphere to the left hemisphere, and that the left hemisphere can represent facial identity but is less efficient at extracting this information by itself.     

Right hemisphere contributions to imitation tasks

Humans imitate biological movements faster than non-biological movements. The faster response has been attributed to an activation of the human mirror neuron system, which is thought to match observation and execution of actions. However, it is unclear which cortical areas are responsible for this behavioural advantage. Also, little is known about the timing of activations. Using whole-head magnetoencephalography we recorded neuronal responses to single biological finger movements and non-biological dot movements while the subjects were required to perform an imitation task or an observation task, respectively. Previous imaging studies on the human mirror neurone system suggested that activation in response to biological movements would be stronger in ventral premotor, parietal and superior temporal regions. In accordance with previous studies, reaction times to biological movements were faster than those to dot movements in all subjects. The analysis of evoked magnetic fields revealed that the reaction time benefit was paralleled by stronger and earlier activation of the left temporo-occipital cortex, right superior temporal area and right ventral motor/premotor area. The activity patterns suggest that the latter areas mediate the observed behavioural advantage of biological movements and indicate a predominant contribution of the right temporo-frontal hemisphere to action observation–execution matching processes in intransitive movements, which has not been reported previously.     

大脑半球多脑叶离断术治疗难治性癫(痫)

目的 介绍一种新的治疗半球性病变引起的难治性癫(痫)的手术方法,并就该于术方法和适应证进行讨论.方法 应用新的大脑半球多脑叶离断术.分步骤离断额叶,颞叶和顶枕叶与丘脑、基底节的联系,通过侧脑室额角和枕角离断胼胝体前后部,只保留中央前后回皮层及其与丘脑、基底节和内囊的联系,治疗一例半球性病变引发的成年难治性癫(痫)患者....     

Right hemisphere advantage for topographical orientation in the domestic chick

When male chicks have to choose whether to orient by distant or proximal cues, chicks using the left eye (and so the right hemisphere) orient far better and make more use of distant cues than do right-eyed chicks. When both eyes are in use, left eye systems are mainly responsible for orientation, whereas right eye systems may concentrate on identifying food. Brief bias towards control of behaviour by the right eye system on day 8 allows it temporarily to be used successfully by the chick for orientation; apparently interference from the left eye system is reduced at this time.     

Right hemisphere advantage for social recognition in the chick.

Recognition of familiar and unfamiliar conspecifics was studied in pair-reared chicks tested binocularly or with only one eye in use. Chicks were tested on day 3 in pairs composed of either cagemates or strangers. Social discrimination, as measured by the ratio "number of pecks at the strangers/total number of pecks" was impaired in right-eyed chicks with respect to left-eyed and binocular chicks. Male chicks showed higher levels of social pecking than females, and chicks that used both eyes showed higher pecking than monocular chicks. There were no significant differences in the total number of pecks (i.e. pecks at companions plus pecks at strangers) between right- and left-eyed chicks: the impairment in social discrimination of right-eyed chicks seemed to be due partly to a reduction in pecking at strangers and partly to an increase in pecking at companions. It is suggested that neural structures fed by the left eye (mainly located at the right hemisphere) are better at processing and/or storing of visual information which allows recognition of individual conspecifics. This may be part of a wider tendency to respond to small changes in any of a variety of intrinsic stimulus properties.