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A variety of lesions in different cerebral regions may affect the human ability to orient in the environment, resulting in ‘topographical disorientation'. In a recent study, we documented the first case of Developmental Topographical Disorientation (DTD), in a person with a life-long inability to orient despite otherwise well-preserved cognitive functions, and in the absence of a cerebral injury/malformation or other neurological condition. This selective topographical disorientation was due to her inability to form a ‘cognitive map', a mental representation of the environment, which in turn impaired her ability to orient in both familiar and unfamiliar surroundings. Here, we describe 120 new cases of DTD recruited via the internet and assessed with an online battery testing their cognitive and orientation skills. We found that people with DTD differ from matched (age, gender and education) healthy controls only in those skills confined to the orientation/navigation domain, among which the ability to form a cognitive map was the most significant factor that distinguished a person affected by DTD from control subjects.

Seamounts are recognized for their biological importance and, more recently, mineral wealth. However, in most cases the biological information required to assess the risk to seamount assemblages from mining is lacking. This study uses towed video footage and environmental data to investigate the patterns of megafaunal distribution, assemblage structure and association with environmental variables, both within and amongst 3 seamounts along the Kermadec volcanic arc in the New Zealand Exclusive Economic Zone. These seamounts represent different levels of hydrothermal activity, with an overlapping depth range: Rumble II East has no history of hydrothermal activity, Brothers is hydrothermally active and Rumble II West is predominantly inactive. All 3 seamounts fall within an area previously licenced for the prospecting phase of seafloor massive sulfide (SMS) mining. In total, 186 putative taxa were identified from video samples and assigned to 20 assemblages. Both seamount and a priori defined habitat (nested within seamount) contributed to explaining variation in assemblage structure, with a mixture of shared and unique assemblages found at each seamount. Magnetivity, as a proxy for hydrothermal activity, explained most of the variation in assemblage structure amongst seamounts, with depth, topography, substratum (and magnetivity for Brothers) explaining most within seamounts. Environmental management implications include the need to designate a network of ‘set-aside’ sites both within and amongst seamounts to adequately protect the range of faunal assemblages present. This study also suggests that inactive SMS areas may support faunal assemblages not found elsewhere within the region and would require suitable protection from mining activities.

Face recognition is generally thought to rely on different neurocognitive mechanisms than most types of objects, but the specificity of these mechanisms is debated. One account suggests the mechanisms are specific to upright faces, whereas the expertise view proposes the mechanisms operate on objects of high within-class similarity with which an observer has become proficient at rapid individuation. Much of the evidence cited in support of the expertise view comes from laboratory-based training experiments involving computer-generated objects called greebles that are designed to place face-like demands on recognition mechanisms. A fundamental prediction of the expertise hypothesis is that recognition deficits with faces will be accompanied by deficits with objects of expertise. Here we present two cases of acquired prosopagnosia, Herschel and Florence, who violate this prediction: Both show normal performance in a standard greeble training procedure, along with severe deficits on a matched face training procedure. Herschel and Florence also meet several response time criteria that advocates of the expertise view suggest signal successful acquisition of greeble expertise. Furthermore, Herschel’s results show that greeble learning can occur without normal functioning of the right fusiform face area, an area proposed to mediate greeble expertise. The marked dissociation between face and greeble expertise undermines greeble-based claims challenging face-specificity and indicates face recognition mechanisms are not necessary for object recognition after laboratory-based training.

In the global effect, saccades are displaced towards a distractor if the latter is near to the target, an effect thought to reflect spatial averaging in neurons of the superior colliculus. The temporal dynamics of the global effect have not been well studied, however. We had twelve subjects perform horizontal saccades to a target in trials in which there were either no distractor or a distractor stimulus located 20° above or below the target. The distractor appeared either simultaneously with the target or preceded it by an interval of between 100 and 800 ms, and was either flashed for only 100 ms or remained visible until the subject responded with a saccade. Both flashed and persistent distractors reduced saccadic latency if they preceded target onset, indicating that subjects could use this cue to prepare saccades in advance. Saccadic endpoint was displaced towards a flashed distractor only if it was simultaneous with the target. However, persistent distractors produced a global effect for both simultaneous presentation and distractor–target intervals of 100 ms, but not for longer intervals. We conclude that the global effect requires of the distractor both a recent onset and persistence of the distractor, and that distractor-related activity decays rapidly within 300 ms.

Foreknowledge about upcoming events may be exploited to optimize behavioural responses. In a previous work, using an eye movement paradigm, we showed that different types of partial foreknowledge have different effects on saccadic efficiency. In the current study, we investigated the neural circuitry involved in processing of partial foreknowledge using functional magnetic resonance imaging. Fourteen subjects performed a mixed antisaccade, prosaccade paradigm with blocks of no foreknowledge, complete foreknowledge or partial foreknowledge about stimulus location, response direction or task. We found that saccadic foreknowledge is processed primarily within the well-known oculomotor network for saccades and antisaccades. Moreover, we found a consistent decrease in BOLD activity in the primary and secondary visual cortex in all foreknowledge conditions compared to the no-foreknowledge conditions. Furthermore we found that the different types of partial foreknowledge are processed in distinct brain areas: response foreknowledge is processed in the frontal eye field, while stimulus foreknowledge is processed in the frontal and parietal eye field. Task foreknowledge, however, revealed no positive BOLD correlate. Our results show different patterns of engagement in the saccade-related neural network depending upon precisely what type of information is known ahead.

The many-to-many hypothesis suggests that face and visual-word processing tasks share neural resources in the brain, even though they show opposing hemispheric asymmetries in neuroimaging and neuropsychologic studies. Recently it has been suggested that both stimulus and task effects need to be incorporated into the hypothesis. A recent study found dual-task interference between face and text functions that lateralized to the same hemisphere, but not when they lateralized to different hemispheres. However, it is not clear whether a lack of interference between word and face recognition would occur for other languages, particularly those with a morpho-syllabic script, like Chinese, for which there is some evidence of greater right hemispheric involvement. Here, we used the same technique to probe for dual-task interference between English text, Chinese characters and face recognition. We tested 20 subjects monolingual for English and 20 subjects bilingual for Chinese and English. We replicated the prior result for English text and showed similar results for Chinese text with no evidence of interference with faces. We also did not find interference between Chinese and English text. The results support a view in which reading English words, reading Chinese characters and face identification have minimal sharing of neural resources.

The anterior cingulate cortex (ACC) participates in both performance optimization and evaluation, with dissociable contributions from dorsal (dACC) and rostral (rACC) regions. Deactivation in rACC and other default-mode regions is important for performance optimization, whereas increased rACC and dACC activation contributes to performance evaluation. Errors activate both rACC and dACC. We propose that this activation reflects differential errorrelated involvement of rACC and dACC during both performance optimization and evaluation, and that these two processes can be distinguished by the timing of their occurrence within a trial. We compared correct and error antisaccade trials. We expected errors to correlate with an early failure of rACC deactivation and increased activation of both rACC and dACC later in the trial. Eighteen healthy subjects performed a series of prosaccade and antisaccade trials during event-related functional MRI. We estimated the hemodynamic responses for error and correct antisaccades using a finite impulse-response model. We examined ACC activity by comparing error and correct antisaccades with a fixation baseline and error to correct antisaccades directly. Compared with correct antisaccades, errors were characterized by an early bilateral failure of deactivation of rACC and other default-mode regions. This difference was significant in rACC. Errors also were associated with increased activity in both rACC and dACC later in the trial. These results show that accurate performance involves deactivation of the rACC and other default mode regions and suggest that both rACC and dACC contribute to the evaluation of error responses.

Whether face adaptation confers any advantages to perceptual processing remains an open question. We investigated whether face adaptation can enhance the ability to make fine discriminations in the vicinity of the adapted face. We compared face discrimination thresholds in three adapting conditions: (i) same-face: where adapting and test faces were the same, (ii) different-face: where adapting and test faces differed, and (iii) baseline: where the adapting stimulus was a blank. Discrimination thresholds for morphed identity changes involving the adapted face (same-face) improved compared with those from both the baseline (no-adaptation) and different-face conditions. Since adapting to a face did not alter discrimination performance for other faces, this effect is selective for the facial identity that is adapted. These results indicate a form of gain control to heighten perceptual sensitivity in the vicinity of a currently viewed face, analogous to forms of adaptive gain control at lower levels of the visual system.

Cerebral visual disorders include a range of common and rare deficits. They can be divided into effects on low-, intermediate-, and high-level forms of visual processing. Low-level deficits are various forms of homonymous hemifield scotomata, which affect all types of vision within their borders. Intermediate-level deficits refer to impairments of colour or motion perception, which affect either one hemifield or the entire field when lesions are bilateral. High-level deficits are divided into those of the ventral (occipitotemporal) or dorsal (occipitoparietal) stream. Occipitotemporal lesions affect various aspects of object recognition, ranging from general visual agnosia to selective agnosias, such as prosopagnosia or topographagnosia from right or bilateral lesions, and pure alexia from left-sided lesions. Occipitoparietal lesions cause the various components of Bálint syndrome, namely, simultanagnosia, optic ataxia, and ocular motor apraxia. They can also cause other impairments of visuospatial or visuotemporal processing, such as astereopsis and sequence-agnosia. Because of anatomic proximity, certain deficits cluster together to form a number of cerebral visual syndromes. Treatment of these disorders remains challenging, with frequent reliance on strategic substitutions rather than restorative approaches.

A preceding antisaccade increases the latency of the saccade in the next trial. Whether this inter-trial effect is generated by the preparation or the execution of the antisaccade is not certain. Our goal was to examine the inter-trial effects from trials on which subjects prepared an antisaccade but did not make one. We tested 15 subjects on blocks of randomly ordered prosaccades and antisaccades. An instructional cue at fixation indicated whether a prosaccade or antisaccade was required, with the target appearing 2 s later. On 20 % of antisaccade trials, the target did not appear (prepared-only antisaccade trials). We analyzed the latencies of all correct prosaccades or antisaccades preceded by correctly executed trials. The latencies of prosaccade trials were 15 ms shorter if they were preceded by prosaccades than if the prior trial was an antisaccade. Prosaccades preceded by trials on which antisaccades were cued but not executed also showed prolonged latencies that were equivalent to those preceded by executed antisaccades. We conclude that the inter-trial effects from a prior antisaccade are generated by its preparation rather than its execution. This may reflect persistence of pre-target preparatory activity from the prior trial to affect that of the next trial in structures like the superior colliculus and frontal eye field.