Cerebral localization of higher functions: The period between Thomas Willis and Paul Broca / Localização cerebral de funções superiores: o período entre Thomas Willis e Paul Broca

ABSTRACT. The age-old debates about the localization of the mind (higher functions) took a new course when Willis located a higher nervous function (memory) in the brain parenchyma, and supposedly, in the cerebral cortex. About two centuries later, Broca, founded on solid scientific reasoning, localized a circumscribed area of the 3rd frontal circumvolution of the left hemisphere as the seat of articulate language, a higher function (speech - language domain). He (and Dax) also defined the functional asymmetry (specialization) of the hemispheres, with left dominance (for language). The period between the findings of these individuals was not quiescent, as numerous authors contributed with their theoretical and clinicopathological research toward creating a conducive scientific atmosphere for this accomplishment, and should be regarded as important. Further studies, in the decades that followed, revealed the localization of additional aspects of language and of other higher functions (cognitive domains).

RESUMO. Os debates milenares sobre a localização da mente (funções superiores) chegaram a um novo caminho quando Willis localizou uma função nervosa superior (memória) no parênquima cerebral, e supostamente, no córtex cerebral. Cerca de dois séculos depois, Broca, baseado em sólido pensamento científico, localizou uma área circunscrita da 3ª circunvolução frontal do hemisfério esquerdo como o sítio da linguagem articulada, uma função superior (fala - domínio da linguagem). Ele (e Dax) também definiu a assimetria funcional (especialização) dos hemisférios, com dominância esquerda (para linguagem). O período entre os achados dessas duas personalidades não ficou quiescente, considerando que numerosos autores contribuíram, com suas pesquisas teóricas e clinicopatológicas, para criar uma atmosfera científica adequada para tal realização, devendo ser vistos como importantes. Mais estudos, nas décadas seguintes, revelaram a localização de aspectos adicionais da linguagem e de outras funções superiores (domínios cognitivos).

Study on the attentional network lateralization in patients with bipolar disorder / 中国神经精神疾病杂志

Objective To investigate the abnormality of cerebral laterality of the three attentional networks (alerting, orienting, executive control) in patients with bipolar depression disorder. Methods Patients with bipolar depression disorder (n=28) and healthy controls (n=40) were selected. Lateralized Attention Network Test (LANT) was used to explore the efficiency of the networks in bilateral cerebral hemisphere. Results In the response time (RT), there was a significant interaction between groups and hemispheres in orienting network (F=4.67, P=0.03). The result of post hoc test indicated that the RT in the orienting function was significantly longer in the left hemisphere than in the right in control group (t=-4.47, P＜0.05). There was no significant difference in the orienting network between the left and right hemisphere in patients with the depressive bipolar disorder. Conclusion Attention is impaired in patients with depressive bipolar disorder in which the disappearance of left hemisphere advantage of orienting network is the main manifestation of attention impairments.

Auditory Cortical Temporal Processing and Hemispheric Asymmetry Revealed by N1 Dipole Source Activity in Adult Cochlear Implant Users / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Cochlear implant (CI) changes the way that sound inputs are processed in the brain, possibly causing brain reorganization. Given that the pattern and degree of reorganization are known to be related to speech perception skill, information regarding hemispheric asymmetry can be used to predict behavioral performances in CI users. The current study investigated the hemispheric asymmetry of N1 dipole cortical activity in response to the temporally varied speech sounds and its relationship to speech perception abilities in adult CI users. SUBJECTS AND METHOD: The cortical activity was recorded from 64 scalp electrodes in 10 CI users and 11 normal-hearing controls. Speech stimuli were synthesized consonant-vowels, the /ba/-/pa/ continuum that ranged from 0 to 50 ms with a 6-step voice onset time (VOT). N1 dipole amplitudes, latencies, and locations were analyzed as a function of VOT and the direction of implantation. Also investigated was the relationship between N1 dipole lateralization and speech perception. RESULTS: For the N1 dipole location, significant location differences between CI and normal hearing groups were seen at 40 ms VOT in the anterior-posterior direction. For hemispheric asymmetry, the N1 dipole activity in good CI performers was higher in the auditory cortex contralateral to the stimulated ear, while poor CI performers showed greater ipsilateral activity. In addition, a lateralization index at 20 ms VOT showed significant correlation with the /ba/-/pa/ consonant perception scores in noise. CONCLUSION: The results suggest that the hemispheric asymmetry of N1 dipole activity in response to stimuli of temporally varied speech has a substantial clinical value, and that this can be used to estimate CI speech perception.

Cerebral Lateralization of Pro- and Anti-Social Tendencies

Mounting evidence suggest that the right-hemisphere (RH) has a relative advantage, over the left-hemisphere (LH), in mediating social intelligence - identifying social stimuli, understanding the intentions of other people, awareness of the dynamics in social relationships, and successful handling of social interactions. Furthermore, a review and synthesis of the literature suggest that pro-social attitudes and behaviors are associated with physiological activity in the RH, whereas unsocial and anti-social tendencies are mediated primarily by the LH. This hemispheric asymmetry is rooted in several neurobiological and functional differences between the two hemispheres. (I) Positive social interactions often require inhibiting one's immediate desires and considering the perspectives and needs of others. Given that self-control is mediated by the RH, pro-social emotions and behaviors are, therefore, inherently associated with the RH as it subserves the brain's self-restraint mechanisms. (II) The RH mediates experiences of vulnerability. It registers the relative clumsiness and motor weakness of the left limbs, and it is involved, more than the LH, in processing threats and mediating fear. Emotional states of vulnerability trigger the need for affiliation and sociality, therefore the RH has a greater role in mediating pro-social attitudes and behaviors. (III) The RH mediates a holistic mode of representing the world. Holistic perception emphasizes similarities rather than differences, takes a long-term perspective, is associated with divergent thinking and seeing other points-of-view, and it mediates a personal mode of relating to people. All these features of holistic perception facilitate a more empathetic attitude toward others and pro-social behaviors.

The Neural Basis of Optimism and Pessimism

Our survival and wellness require a balance between optimism and pessimism. Undue pessimism makes life miserable; however, excessive optimism can lead to dangerously risky behaviors. A review and synthesis of the literature on the neurophysiology subserving these two worldviews suggests that optimism and pessimism are differentially associated with the two cerebral hemispheres. High self-esteem, a cheerful attitude that tends to look at the positive aspects of a given situation, as well as an optimistic belief in a bright future are associated with physiological activity in the left-hemisphere (LH). In contrast, a gloomy viewpoint, an inclination to focus on the negative part and exaggerate its significance, low self-esteem as well as a pessimistic view on what the future holds are interlinked with neurophysiological processes in the right-hemisphere (RH). This hemispheric asymmetry in mediating optimistic and pessimistic outlooks is rooted in several biological and functional differences between the two hemispheres. The RH mediation of a watchful and inhibitive mode weaves a sense of insecurity that generates and supports pessimistic thought patterns. Conversely, the LH mediation of an active mode and the positive feedback it receives through its motor dexterity breed a sense of confidence in one's ability to manage life's challenges, and optimism about the future.

Normative study of tympanic infrared thermometry: a non-invasive index of asymmetric cerebral activity

Human and primate studies have demonstrated that performance of tasks that induce asymmetrical physiological activation of the cerebral hemispheres leads to a reduction of tympanic temperature (TT) ipsilateral to the most active hemisphere. It is possible that diseases that interfere in an asymmetrical fashion with the degree of cerebral activity cause similar TT changes. There are not, however, normative studies of the acceptable interaural difference in TT in normal subjects at rest. This study was done to establish normative values for interaural TT values measured by means of infrared tympanic thermometry in resting normal subjects not engaged in any specific task. TT values were measured in 47 normal volunteers (20 men and 27 women, aged 39.38±12.57 years old) at rest; mean interaural differences of TT were calculated. Mean right ear TT was 36.85±0.50ºC and mean left ear TT was 36.74±0.57ºC; these values are in agreement with those already reported in the literature. Mean interaural TT difference was 0.25ºC (SD 0.21ºC). These findings indicate that maximal normal values for interaural TT differences, with confidence levels of 99 percent and 95 percent, are, respectively, 0.88 and 0.67ºC. The value of interaural differences of TT as a marker of asymmetrical hemispheric activity in neurological patients will have to be established by additional studies.

Estudos em humanos e outros primatas demonstraram que a realização de tarefas que causam ativação assimétrica fisiológica dos hemisférios cerebrais resulta em redução da temperatura timpânica (TT) ipsilateral ao hemisfério cerebral mais ativo. É possível que patologias que interfiram de modo assimétrico com o grau de atividade cerebral causem alterações similares da TT. Não existem, entretanto, estudos normativos da diferença normal aceitável de TT entre os tímpanos de um mesmo indivíduo em repouso. Este estudo teve como objetivo estabelecer uma normatização dos valores bilaterais da TT, e principalmente das diferenças interauriculares desse parâmetro, obtidas por termometria timpânica por infravermelho, em indivíduos normais, na ausência de execução de tarefas específicas. Foram obtidas medidas da TT em 47 voluntários normais (20 homens e 27 mulheres, com média de idade de 39,38±12,57 anos) em repouso e calculadas as diferenças interauriculares, sua média e desvio-padrão. A TT média foi de 36,85±0,50ºC à direita e de 36,74± 0,57ºC à esquerda, o que está de acordo com dados da literatura. A média das diferenças de TT encontrada foi de 0,25ºC e o desvio padrão (DP) 0,21ºC. Com base nesses achados, os valores máximos considerados normais para a diferença interauricular da TT, com níveis de confiança de 99 por cento e de 95 por cento, são de 0,88ºC e 0,67ºC, respectivamente. A utilidade da medida da diferença interauricular da TT como marcador de assimetria da atividade cerebral em pacientes com patologias neurológicas deverá ser avaliada em estudos adicionais.

Hemispheric Asymmetry of Median Nerve Somatosensory Evoked Potential

OBJECTIVE: To elucidate interhemispheric asymmetry of the neural generators of somatosensory evoked potential (SEP). METHOD: Median nerve SEP was recorded over 5 sites of each hemisphere in 20 healthy subjects and 23 stroke patients. One electrode was placed over C3'/C4' (position B) and two electrodes were located 2 cm medial (position A) and lateral (position C) to position B, respectively. Additional two electrodes were positioned at 3 cm anterior (position F) and posterior (position P) to position B. The common reference electrode was placed at Fz. RESULTS: In healthy subjects, P22 was more frequently evoked than P27 in position F of the nondominant hemisphere and P27 in position P of the dominant hemisphere. In stroke subjects, fourteen patients demonstrated SEP waveforms over the affected hemisphere. In them, SEP amplitude significantly correlated with proprioception. However, distribution of the recording position showing significant correlation between SEP amplitude and proprioception was different according to dominancy of the affected hemisphere. CONCLUSION: P22 was more dominant in the nondominant hemisphere and P27 in the dominant hemisphere of normal group. Furthermore, clinical correlation of SEP amplitude was affected by the injured hemisphere dominancy in stroke group. These results demonstrate that asymmetry of neural generator distribution can be presumed.