Reciprocal anatomical relationship between primary sensory and prefrontal cortices in the human brain

The human brain exhibits remarkable interindividual variability in cortical architecture. Despite extensive evidence for the behavioral consequences of such anatomical variability in individual cortical regions, it is unclear whether and how different cortical regions covary in morphology. Using a novel approach that combined noninvasive cortical functional mapping with whole-brain voxel-based morphometric analyses, we investigated the anatomical relationship between the functionally mapped visual cortices and other cortical structures in healthy humans. We found a striking anticorrelation between the gray matter volume of primary visual cortex and that of anterior prefrontal cortex, independent from individual differences in overall brain volume. Notably, this negative correlation formed along anatomically separate pathways, as the dorsal and ventral parts of primary visual cortex showed focal anticorrelation with the dorsolateral and ventromedial parts of anterior prefrontal cortex, respectively. Moreover, a similar inverse correlation was found between primary auditory cortex and anterior prefrontal cortex, but no anatomical relationship was observed between other visual cortices and anterior prefrontal cortex. Together, these findings indicate that an anatomical trade-off exists between primary sensory cortices and anterior prefrontal cortex as a possible general principle of human cortical organization. This new discovery challenges the traditional view that the sizes of different brain areas simply scale with overall brain size and suggests the existence of shared genetic or developmental factors that contributes to the formation of anatomically and functionally distant cortical regions

Perceptual organization and consciousness

With chapter written by leading researchers in the field, this is the state-of-the-art reference work on this topic, and will be so for many years to come

Hinnehmen, aber nicht schweigen. Plädoyer für einen unaufgeregten Umgang mit Religionskritik in den Medien

"Sie werden keine einzige, ich will nicht sagen christliche, ich sage nicht katholische, sondern ledigüch gesittete Nation antreffen, die auf grobe Beleidigung ihrer Religion nicht die Todesstrafe gesetzt hätte". Dies schrieb der bedeutende Theoretiker der Reaktion Joseph Graf de Maistre am 15. Juli 1815 in einem seiner "Briefe an einen russischen Edelmann über die spanische Inquisition". Heute zählt man Länder, die sich derart verhalten, nicht zu den gesitteten. Das gilt auch für Afghanistan, wo der Rat höchster islamischer religiöser Gelehrter die Hinrichtung eines Studenten wegen Beleidigung des Islam empfahl, weil er einen Artikel über Frauenrechte im Islam aus dem Internet heruntergeladen, ausgedruckt und unter Studenten verteilt hatte. Nach Pressemeldungen hat der afghanische Senat das Urteil rechtskräftig bestätigt. Beleidigung des Islam ist dort ausdrücklich von der ansonsten in der Verfassung garantierten Freiheit der Medien ausgenommen. (...)

Ideologiepolizei, Spionagedienst, Desinformationsagentur. Die Stasi und die Medien in Ost und West

Eines der wichtigsten Felder, auf denen der Staatsicherheitsdienst der Deutschen Demokratischen Republik seinen politischen Auftrag und sein Selbstverständnis (beides zusammengefasst in der Devise „Schild und Schwert der Partei“) zu verwirklichen hatte, waren die Medien, vornehmlich Hörfunk und Fernsehen. Dieser Schwerpunkt ergab sich einmal aus der Einschätzung, dass die beiden Medien bei der Erziehung der DDR-Bevölkerung zum Sozialismus von außerordentlicher Bedeutung und Wirksamkeit seien (oder zu sein hätten), zum anderen aus der Tatsache, dass der Zugang der Erziehungsadressaten zu westdeutschem Hörfunk und Fernsehen einschließlich der sich daraus ergebenden Folgen für das politische Bewusstsein der DDR-Bevölkerung nicht zu verhindern sei. Vorrangig war danach nicht die unverzügliche Bekehrung der Bevölkerung der Bundesrepublik Deutschland zum Sozialismus, sondern die Festigung des Glaubens der Deutschen in der DDR an die sozialistische Idee, ihrer Einsicht in die Vortrefflichkeit der vorhandenen und mehr noch der verheißenen konkreten sozialistischen Ordnung sowie die Zerstörung der Annahme, dass der Weg der Bundesrepublik der für die Bürger bessere sei. (...

Variability in visual cortex size reflects tradeoff between local orientation sensitivity and global orientation modulation

The surface area of early visual cortices varies several fold across healthy adult humans and is genetically heritable. But the functional consequences of this anatomical variability are still largely unexplored. Here we show that interindividual variability in human visual cortical surface area reflects a tradeoff between sensitivity to visual details and susceptibility to visual context. Specifically, individuals with larger primary visual cortices can discriminate finer orientation differences, whereas individuals with smaller primary visual cortices experience stronger perceptual modulation by global orientation contexts. This anatomically correlated tradeoff between discrimination sensitivity and contextual modulation of orientation perception, however, does not generalize to contrast perception or luminance perception. Neural field simulations based on a scaling of intracortical circuits reproduce our empirical observations. Together our findings reveal a feature-specific shift in the scope of visual perception from context-oriented to detail-oriented with increased visual cortical surface area

Weighting of binocular experience in visual cortical development

After birth the brain adapts to characteristics in the environment in order to optimise its resources with respect to the individual's circumstances. For instance, early monocular deprivation results in reduced cortical representation and visual acuity of the deprived eye. However, such a loss of visual function in one eye after only transient periods of compromised vision through injury or infection would seem to be maladaptive. I examined here whether cortical deprivation effects can be counteracted by daily periods of normal experience. Cats received variable daily regimens of monocular deprivation (by wearing a mask) and binocular exposure. Visual cortex function was subsequently assessed with optical imaging of intrinsic signals, visually evoked potentials, and extracellular electrophysiological recordings. Regardless of the overall length of visual experience, daily binocular vision for as little as 30 minutes, but no less, allowed normal ocular dominance and visual responses to be maintained despite several times longer periods of deprivation. Thus, the absolute amount of daily binocular vision rather than its relative share of the total daily exposure determined the outcome. When 30 minutes binocular exposure were broken up into two 15-minute blocks flanking the deprivation period, ocular dominance resembled that of animals with only 15 minutes binocular vision, suggesting that binocular experience must be continuous to be most effective. My results demonstrate that normal experience is clearly more efficacious in maintaining a binocular visual cortex than abnormal experience is in shifting the ocular dominance distribution. These findings con tribute to the larger debate about how much nature and nurture, respectively, contribute to the development of the brain they suggest that while experience plays a significant role, for some functions there may be an intrinsic bias towards a state that is optimally adapted to the most probable environment.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Investigating Representations of Facial Identity in Human Ventral Visual Cortex with Transcranial Magnetic Stimulation

The occipital face area (OFA) is face-selective. This enhanced activation to faces could reflect either generic face and shape-related processing or high-level conceptual processing of identity. Here we examined these two possibilities using a state-dependent transcranial magnetic stimulation (TMS) paradigm. The lateral occipital (LO) cortex which is activated non-selectively by various types of objects served as a control site. We localized OFA and LO on a per-participant basis using functional MRI. We then examined whether TMS applied to either of these regions affected the ability of participants to decide whether two successively presented and physically different face images were of the same famous person or different famous people. TMS was applied during the delay between first and second face presentations to investigate whether neuronal populations in these regions played a causal role in mediating the behavioral effects of identity repetition. Behaviorally we found a robust identity repetition effect, with shorter reaction times (RTs) when identity was repeated, regardless of the fact that the pictures were physically different. Surprisingly, TMS applied over LO (but not OFA) modulated overall RTs, compared to the No-TMS condition. But critically, we found no effects of TMS to either area that were modulated by identity repetition. Thus, we found no evidence to suggest that OFA or LO contain neuronal representations selective for the identity of famous faces which play a causal role in identity processing. Instead, these brain regions may be involved in the processing of more generic features of their preferred stimulus categories

Weighting of binocular experience in visual cortical development.

After birth the brain adapts to characteristics in the environment in order to optimise its resources with respect to the individual's circumstances. For instance, early monocular deprivation results in reduced cortical representation and visual acuity of the deprived eye. However, such a loss of visual function in one eye after only transient periods of compromised vision through injury or infection would seem to be maladaptive. I examined here whether cortical deprivation effects can be counteracted by daily periods of normal experience. Cats received variable daily regimens of monocular deprivation (by wearing a mask) and binocular exposure. Visual cortex function was subsequently assessed with optical imaging of intrinsic signals, visually evoked potentials, and extracellular electrophysiological recordings. Regardless of the overall length of visual experience, daily binocular vision for as little as 30 minutes, but no less, allowed normal ocular dominance and visual responses to be maintained despite several times longer periods of deprivation. Thus, the absolute amount of daily binocular vision rather than its relative share of the total daily exposure determined the outcome. When 30 minutes binocular exposure were broken up into two 15-minute blocks flanking the deprivation period, ocular dominance resembled that of animals with only 15 minutes binocular vision, suggesting that binocular experience must be continuous to be most effective. My results demonstrate that normal experience is clearly more efficacious in maintaining a binocular visual cortex than abnormal experience is in shifting the ocular dominance distribution. These findings con tribute to the larger debate about how much nature and nurture, respectively, contribute to the development of the brain; they suggest that while experience plays a significant role, for some functions there may be an intrinsic bias towards a state that is optimally adapted to the most probable environment

Literatur-Rundschau

Dieter Stolte: Wie das Fernsehen das Menschenbild verändert (Dietrich Schwarzkopf)Paul-Gerhard Roller: Das Wesen des Christentums als mediale Wirklichkeit (Steffen W. Hillebrecht)Hans-Jürgen Jacobs/Wolfgang R. Langenbucher (Hg.): Das Gewissen ihrer Zeit. Fünfzig Vorbilder des Journalismus (Christian Klenk)Sebastian Haffner: Das Leben der Fußgänger. Feuilletons 1933-1938 (Verena Blaum