Start | basic neuroanat. | reading | zeki extracts | table of links | List of Refs | Journals
   [no longer on paper handout]

Corina, D. P., Jose-Robertson, L. S., Guillemin, A., High, J., & Braun, A. R. (2003). Language lateralization in a bimanual language. Journal of Cognitive Neuroscience, 15(5), 718-730.

Unlike spoken languages, sign languages of the deaf make use of two primary articulators, the right and left hands, to produce signs, This situation has no obvious parallel in spoken languages, in which speech articulation is carried out by symmetrical unitary midline vocal structures. This arrangement affords a unique opportunity to examine the robustness of linguistic systems that underlie language production in the face of contrasting articulatory demands and to chart the differential effects of handedness for highly skilled movements. Positron emission tomography (PET) technique was used to examine brain activation in 16 deaf users of American Sign Language (ASL) while subjects generated verb signs independently with their right dominant and left nondominant hands (compared to the repetition of noun signs), Nearly identical patterns of left inferior frontal and right cerebellum activity were observed. This pattern of activation during signing is consistent with patterns that have been reported for spoken languages including evidence for specializations of inferior frontal regions related to lexical- semantic processing, search and retrieval, and phonological encoding. These results indicate that lexical-semantic processing in production relies upon left-hemisphere regions regardless of the modality in which a language is realized, and that this left- hemisphere activation is stable, even in the face of conflicting articulatory demands. in addition, these data provide evidence for the role of the right posterolateral cerebellum in linguistic-cognitive processing and evidence of a left ventral fusiform contribution to sign language processing.gif

Harris, I. M., & Miniussi, C. (2003). Parietal lobe contribution to mental rotation demonstrated with rTMS. Journal of Cognitive Neuroscience, 15(3), 315-323.

A large number of imaging studies have identified a role for the posterior parietal lobe, in particular Brodmann's area 7 and the intraparietal sulcus (IPS), in mental rotation. Here we investigated whether neural activity in the posterior parietal lobe is essential for successful mental rotation performance by observing the effects of interrupting this activity during the execution of a mental rotation task. Repetitive transcranial magnetic stimulation (rTMS) was applied to posterior parietal locations estimated to overlie Brodmann's area 7 in the right and the left hemisphere, or to a posterior midline location (sham condition). In three separate experiments, rTMS (four pulses, 20 Hz) was delivered at these locations either 200-400, 400-600, or 600-800 msec after the onset of a mental rotation trial. Disrupting neural activity in the right parietal lobe interfered with task performance, but only when rTMS was delivered 400 to 600 msec after stimulus onset. Stimulation of the left parietal lobe did not reliably affect mental rotation performance at any of the time points investigated. The time- limited effect of rTMS was replicated in a fourth experiment that directly compared the effects of rTMS applied to the right parietal lobe either 200-400 or 400-600 msec into the mental rotation trial. The results indicate that the right superior posterior parietal lobe plays an essential role in mental rotation, consistent with its involvement in a variety of visuospatial and visuomotor transformations.gif

Hunter, M. D., Griffiths, T. D., Farrow, T. F. D., Zheng, Y., Wilkinson, I. D., Hegde, N., Woods, W., Spence, S. A., & Woodruff, P. W. R. (2003). A neural basis for the perception of voices in external auditory space. Brain, 126, 161-169.

We used functional imaging of normal subjects to identify the neural substrate for the perception of voices in external auditory space. This fundamental process can be abnormal in psychosis, when voices that are not true external auditory objects (auditory verbal hallucinations) may appear to originate in external space. The perception of voices as objects in external space depends on filtering by the outer ear. Psychoses that distort this process involve the cerebral cortex. Functional magnetic resonance imaging was carried out on 12 normal subjects using an inside-the-scanner simulation of 'inside head' and 'outside head' voices in the form of typical auditory verbal hallucinations. Comparison between the brain activity associated with the two conditions allowed us to test the hypothesis that the perception of voices in external space ('outside head') is subserved by a temperoparietal network comprising association auditory cortex posterior to Heschl's gyrus [planum temporale (PT)] and inferior parietal lobule. Group analyses of response to 'outside head' versus 'inside head' voices showed significant activation solely in the left PT. This was demonstrated in three experiments in which the predominant lateralization of the stimulus was to the right, to the left or balanced. These findings suggest a critical involvement of the left PT in the perception of voices in external space that is not dependent on precise spatial location. Based on this, we suggest a model for the false perception of externally located auditory verbal hallucinations.gif

Noppeney, U., Friston, K. J., & Price, C. J. (2003). Effects of visual deprivation on the organization of the semantic system. Brain, 126, 1620-1627.

Early onset blindness provides a lesion model to investigate whether experience-dependent mechanisms subtend the functional anatomy of semantic retrieval. In particular, visual deprivation might alter the neural systems underlying retrieval of semantic information that is acquired via visual experience. Using functional MRI, we demonstrate that both early blind and sighted subjects activate a left-lateralized fronto-temporal 'core' semantic retrieval system and show common effects for retrieval of visually experienced semantic information. However, irrespective of the type of semantics, blind subjects activate additional extrastriate regions, which are coupled with frontal and temporal semantic regions. The resilience of semantic retrieval responses to visual deprivation suggests a considerable degree of innate and epigenetic specification of the semantic system. In contrast, the exuberant functional connectivity between extrastriate and 'core' semantic retrieval regions might be explained by abnormal pruning processes during early neurodevelopment. gif

Piefke, M., Weiss, P. H., Zilles, K., Markowitsch, H. J., & Fink, G. R. (2003). Differential remoteness and emotional tone modulate the neural correlates of autobiographical memory. Brain, 126, 650-668.

Autobiographical memory relies on complex interactions between episodic memory contents, associated emotions and a sense of self-continuity along the time axis of one's life history. The neural correlates underlying autobiographical memory are known to primarily comprise areas of prefrontal cortex, medial and lateral temporal cortex, as well as posterior cingulate and retrosplenial cortex. By contrast, the effect of encoding and/or storage parameters such as the emotional tone of the memories retrieved or the length of the time-interval between the initial encoding of information and retrieval remains to be clarified. …we investigated the impact of remoteness and emotional valence on the neural correlates of autobiographical memory retrieval. Changes in neural activity related to autobiographical memory retrieval (irrespective of remoteness and emotional tone) relative to baseline were observed bilaterally in medial and lateral temporal, temporal- occipital, posterior cingulate and frontal cortices. Recent (relative to remote) memories were associated with differentially increased neural activity bilaterally in the retrosplenial cortex and the hippocampal region, whereas remote (relative to recent) memories did not show any statistically significant differential neural activations. Positive (relative to negative) memories bilaterally activated the orbitofrontal cortex, the temporal pole, as well as medial temporal areas, with the activation peak being in the entorhinal region. By contrast, negative (relative to positive) memories differentially increased neural activity in the right middle temporal gyrus only. The data suggest differential functional roles for temporal, prefrontal and retrosplenial regions during autobiographical memory retrieval depending on the remoteness and the emotional valence of the memories retrieved. In particular, our findings support the 'classic' model of long-term memory processing, which suggests a time-limited differential involvement of the hippocampus in memory consolidation. Interestingly, the observation of such a time-dependent involvement of the hippocampal region in memory consolidation corresponds to the course of retrograde amnesia observed in demented patients, with the loss of recent memories appearing during early stages of the disease.. Only during later stages do remote memories also become impaired. We conclude that the brain regions involved in autobiographical memory retrieval are influenced by the triggered memories' emotional significance and their relationship to the individual time axis.

Usui, K., Ikeda, A., Takayama, M., Matsuhashi, M., Yamamoto, J. I., Satoh, T., Begum, T., Mikuni, N., Takahashi, J. B., Miyamoto, S., Hashimoto, N., & Shibasaki, H. (2003). Conversion of semantic information into phonological representation: a function in left posterior basal temporal area. Brain, 126, 632-641.

A unique feature of Japanese language is that its written sentences consist of both morphograms (kanji) and syllabograms (kana). Despite extensive research by PET, functional MRI and MEG, the issues of the difference (or the similarities) between the processing of kanji and kana, and between word reading and object/picture naming have not been resolved as yet. This study investigated the function of the posterior basal temporal area in the language dominant hemisphere in auditory and visual language processing, with special emphasis on semantic and phonological recognition. Subdural electrode grids were placed on the left temporal area of a right-handed woman with intractable temporal lobe epilepsy as part of a pre-surgical evaluation. Her dominant hemisphere for language was shown to be the left on the Wada test. Electric stimulation of 50 Hz was applied to the electrodes during the tasks related to language. Our results showed a clear distinction in the responses and/or performance of the subject depending on the type of characters presented and the tasks employed. Electric stimulation of a localized area in the posterior basal temporal lobe caused neither comprehensive nor productive deficit in the tasks using auditory stimuli. In the tasks using visual stimuli, in contrast, impairments were observed in (i) reading of kanji words and (ii) naming of objects/pictures and geometric designs, but not in (iii) reading of kana, (iv) copying of kanji, kana and geometric designs, and (v) using tools. The subject maintained full comprehension of spoken language, suggesting that the auditory tasks are not processed in the posterior basal temporal area. The fact that the impairment of kanji reading and disturbance of object/picture naming were elicited by electric stimulation of the same area indicates that there is at least one anatomical area that is used commonly for kanji (but not kana) and object processing. The conceptual entity of the test items supposedly was recognized correctly, but the concept failed to be matched to correct phonological representation. The left posterior basal temporal area, therefore, has an important function of connecting visual semantic information into phonological representation.

[not on handout]

Start | basic neuroanat. | reading | zeki extracts | table of links | List of Refs | Journals