Material type and attention control in dichotic listening

The present study investigated the effects of semantic and emotional content on laterality effects found in focused attention dichotic listening tasks. A total of 80 right-handed participants completed one of four conditions. They were presented either with dichotic pairs of consonant-vowel (CV) syllables (ba, da, ga, ka, pa, or ta) or words (bower, dower, power, or tower), pronounced in either a neutral tone or one of four emotional tones (happy, sad, angry, neutral). In all conditions, participants were instructed to circle the stimulus presented to the attended ear on each trial. The attended ear was randomised between blocks of trials for each participant. A significant condition by ear attended by ear of presentation interaction emerged. The typical right ear advantage (REA) was found in the neutral conditions, regardless of ear attended. In contrast, the emotional conditions revealed an REA when participants focused on the right ear, whereas a left ear advantage was found when they focused on the left ear. These findings suggest that the emotional component resulted in a shift in ear advantage coinciding with instructions possibly because of the influence of this component on attention and task difficulty. The role of semantic processing in words versus syllables is also discussed.     

Abstracts of oral presentations,presented at the British Neuropsychological Society (BNS) spring meeting,April 2002, National Hospital,Queen Square,London, UK

Abstract

Visuo-spatial neglect can be conceptualized as a failure of right hemisphere global attentional systems to direct the visual processor of the left hemisphere uniformly across an array. Two patients have recently been reported who show a dissociation of preserved global visual form perception in the context of left neglect for constituent elements. We present the first longitudinal study of the phenomenon which confirms that this pattern of neglect is associated with extensive right hemisphere damage, is fairly stable over time and may persist up to one year post insult. The use of modified Navon figures suggests that task demands may be significant in the manifestation of neglect. Correlation with conventional diagnostic tests for neglect is poor, but results suggest a subgroup of Navon stimuli that may be particularly sensitive to clinical change.     

Auditory temporal envelope processing in a patient with left-hemisphere damage

Abstract

Auditory temporal envelope processing was investigated in a patient showing a mild speech identification impairment following left-hemisphere damage. Three tasks evaluated the patient's ability to: (1) detect a sinusoidal amplitude modulation (SAM) applied to a white noise, as a function of modulation rate (i.e. her ‘temporal modulation transfer function’ or TMTF); (2) discriminate between two white noises amplitude modulated by time-reversed temporally asymmetric envelopes; and (3) identify white noises amplitude modulated by the temporal envelope of speech stimuli. Measurements of intensity discrimination thresholds were performed as a control task. Compared to normal data, the results obtained with the brain-damaged patient showed: (1) increased thresholds for the detection of SAM; (2) increased thresholds for the discrimination of temporal asymmetry; and (3) a deficit in the identification of speechenvelope noise stimuli. In contrast, intensity discrimination thresholds were within the normal range. Taken together, the results indicate a general impairment in auditory temporal acuity, which is now specified as a deficit in the coding of envelope rate and shape, and a deficit in the ability to use temporal envelope cues in speech processing. These results support the hypothesis that left-hemisphere damage is associated with an impairment in time analysis, which may cause, in turn, speech intelligibility disorders.     

Semantic organisation and handedness: Mixed-handedness is associated with more diffuse activation of ambiguous word associates

Research indicates that there are individual differences in the flexibility and ease with which one retrieves and uses concepts stored in memory. Based on prior research suggesting that mixed-handedness is associated with greater cognitive flexibility, it was hypothesised that mixed-handers have access to a relatively diffuse associative network, where link strengths for closely related and distantly related concepts are not as disparate as in the case of strong-handers. This idea was explored using ambiguous words for stimuli, as ambiguous words are known to have both strong (concepts related via dominant meaning) and weak associates (concepts related via subordinate meaning). Consistent with the prediction, mixed-handers showed equal ease in accessing both strongly and weakly related concepts. In Experiment 1 mixed-handers exhibited equivalent priming for dominant and subordinate associates, while strong-handers exhibited priming for dominant associates only. In Experiment 2 ratings of strength of association for dominant versus subordinate associates were examined. Mixed-handedness was associated with lesser disparity of dominant and subordinate association ratings.     

The lighter side of advertising: Investigating posing and lighting biases

People tend to display the left cheek when posing for a portrait; however, this effect does not appear to generalise to advertising. The amount of body visible in the image and the sex of the poser might also contribute to the posing bias. Portraits also exhibit lateral lighting biases, with most images being lit from the left. This effect might also be present in advertisements. A total of 2801 full-page advertisements were sampled and coded for posing direction, lighting direction, sex of model, and amount of body showing. Images of females showed an overall leftward posing bias, but the biases in males depended on the amount of body visible. Males demonstrated rightward posing biases for head-only images. Overall, images tended to be lit from the top left corner. The two factors of posing and lighting biases appear to influence one another. Leftward-lit images had more leftward poses than rightward, while the opposite occurred for rightward-lit images. Collectively, these results demonstrate that the posing biases in advertisements are dependent on the amount of body showing in the image, and that biases in lighting direction interact with these posing biases.     

术中超声实时导航在大脑半球肿瘤切除术中的应用

目的比较术前MR图像与术中超声图像对手术指导的差异,评价术中B超的应用价值。方法回顾性分析26例应用术前1.5T场强MRI及术中超声辅助切除的大脑半球肿瘤患者,对比两种方法对肿瘤血供的探测能力和对肿瘤边界大小的判断能力的差异。结果对肿瘤的血供判断方面,术中B超有探测能力强,实时、随时探测的术中指导能力;对肿瘤的大小边界判断方面,术中B超判断边界与MR图像无统计学差别,虽然图像清晰度不及MR图像,但由于其实时探测能力而在手术中更具实时指导的优越性。结论对于大脑半球肿瘤,术中超声辅助切除能有效提高无创探查效率,减少神经损伤,及早控制肿瘤供血,指导肿瘤全切。     

Transcranial random noise stimulation (tRNS) over prefrontal cortex does not influence the evaluation of facial emotions

ABSTRACT

Cerebral asymmetries for emotion processing are controversial, the right hemisphere being considered either superior in the recognition of all emotions, or superior in the recognition of negative emotions (together with the left-hemispheric superiority for positive emotions). In a number of previous studies, tDCS was applied on the left/right prefrontal cortex (PFC) in order to disentangle this issue, but the results remain controversial. We applied hf-tRNS/sham stimulation over the left/right PFC, during the presentation of neutral, angry and happy faces presented as broadband images (supraliminal condition), and as “hybrid” stimuli in which an emotional face in low spatial frequency is superimposed to the neutral expression of the same individual in high spatial frequency (subliminal condition), during a friendliness evaluation task. The results showed that angry and happy unfiltered stimuli were judged as the most unfriendly and friendly, respectively. Importantly, we found that hf-tRNS applied over the left/right PFC did not influence friendliness evaluations for emotional faces.     

Depression and partial epilepsy: Relevance of laterality of the epileptic focus

Abstract

In a prospective study of 50 epileptic patients (20 with a left hemisphere epileptic focus, 20 with a right one and 10 with a cryptogenic generalized epilepsy), the authors show that depression as appreciated by the H.A.R.D. score, is more frequent and severe in partial epilepsy in males, and when the epileptic focus is localized on left hemisphere. This association is related to the duration of epilepsythe number of seizures, but not to age or medication status.. Vulnerability of left hemisphere to depression is analysedand neuro-chemical mechanisms are discussed. [Neurol Res 1993; 15: 136-138]