Predictive feedback and conscious visual experience

The human brain continuously generates predictions about the environment based on learned regularities in the world. These predictions actively and efficiently facilitate the interpretation of incoming sensory information. We review evidence that, as a result of this facilitation, predictions directly influence conscious experience. Specifically, we propose that predictions enable rapid generation of conscious percepts and bias the contents of awareness in situations of uncertainty. The possible neural mechanisms underlying this facilitation are discussed.

Perampanel Study 207: long-term open-label evaluation in patients with epilepsy

OBJECTIVES

Evaluate interim long-term tolerability, safety and efficacy of adjunctive perampanel, a novel α-amino-3-hydroxy-5-methyl-5-isoxazolepropionic acid (AMPA)-receptor antagonist, in patients with refractory partial-onset seizures.

MATERIALS AND METHODS

Study 207, an open-label extension (OLE) study (ClinicalTrials.gov identifier: NCT00368472), enrolled patients (18-70 years) who completed one of two randomized, placebo-controlled, dose-escalation Phase II studies. The OLE Treatment Phase comprised a 12-week Titration Period (2 mg increments of perampanel every 2 weeks to 12 mg/day, maximum) and a Maintenance Period, during which patients continued treatment up to a planned maximum of 424 weeks (~8 years). Interim analysis data cut-off date was 1 December, 2010.

RESULTS

Of 180 patients completing the Phase II studies, 138 enrolled in study 207. At the time of interim analyses (approximately 4 years after study start), over a third (n = 53, 38.4%) remained on perampanel; 41.3% (n = 57) of patients had >3 years of exposure; and 13.0% (n = 18) had at least 4 years' exposure. Mean ± standard deviation (SD) duration of exposure was 116 ± 75 weeks and mean ± SD dose during the OLE Maintenance Period was 7.3 ± 3.3 mg. No new safety signals emerged with long-term treatment. Consistent with previous studies, the most common treatment-emergent adverse events were as follows: dizziness, headache and somnolence. Overall median (range) per cent change from baseline in seizure frequency per 28 days during open-label treatment was -31.5% (-99.2 to 512.2).

CONCLUSIONS

Long-term - up to 4 years - adjunctive perampanel had a favourable tolerability profile in patients with refractory partial-onset seizures. Improvements in seizure control were maintained with long-term treatment.

Contributions of low and high spatial frequency processing to impaired object recognition circuitry in schizophrenia

Patients with schizophrenia exhibit cognitive and sensory impairment, and object recognition deficits have been linked to sensory deficits. The "frame and fill" model of object recognition posits that low spatial frequency (LSF) information rapidly reaches the prefrontal cortex (PFC) and creates a general shape of an object that feeds back to the ventral temporal cortex to assist object recognition. Visual dysfunction findings in schizophrenia suggest a preferential loss of LSF information. This study used functional magnetic resonance imaging (fMRI) and resting state functional connectivity (RSFC) to investigate the contribution of visual deficits to impaired object "framing" circuitry in schizophrenia. Participants were shown object stimuli that were intact or contained only LSF or high spatial frequency (HSF) information. For controls, fMRI revealed preferential activation to LSF information in precuneus, superior temporal, and medial and dorsolateral PFC areas, whereas patients showed a preference for HSF information or no preference. RSFC revealed a lack of connectivity between early visual areas and PFC for patients. These results demonstrate impaired processing of LSF information during object recognition in schizophrenia, with patients instead displaying increased processing of HSF information. This is consistent with findings of a preference for local over global visual information in schizophrenia.

The effect of mental progression on mood

Mood affects the way people think. But can the way people think affect their mood? In the present investigation, we examined this promising link by testing whether mood is influenced by the presence or absence of associative progression by manipulating the scope of participants' information processing and measuring their subsequent mood. In agreement with our hypothesis, processing that involved associative progression was associated with relatively better moods than processing that was restricted to a single topic (Experiment 1). Experiment 2 ruled out the possibility that conceptual plurality alone accounted for these mood differences; results converge with the view that mood is affected by the degree to which thoughts advance conceptually.

Micro-valences: perceiving affective valence in everyday objects

Perceiving the affective valence of objects influences how we think about and react to the world around us. Conversely, the speed and quality with which we visually recognize objects in a visual scene can vary dramatically depending on that scene’s affective content. Although typical visual scenes contain mostly “everyday” objects, the affect perception in visual objects has been studied using somewhat atypical stimuli with strong affective valences (e.g., guns or roses). Here we explore whether affective valence must be strong or overt to exert an effect on our visual perception. We conclude that everyday objects carry subtle affective valences – “micro-valences” – which are intrinsic to their perceptual representation.

Enabling global processing in simultanagnosia by psychophysical biasing of visual pathways

A fundamental aspect of visual cognition is our disposition to see the 'forest before the trees'. However, damage to the posterior parietal cortex, a critical brain region along the dorsal visual pathway, can produce a neurological disorder called simultanagnosia, characterized by a debilitating inability to perceive the 'forest' but not the 'trees' (i.e. impaired global processing despite intact local processing). This impairment in perceiving the global shape persists even though the ventral visual pathway, the primary recognition pathway, is intact in these patients. Here, we enabled global processing in patients with simultanagnosia using a psychophysical technique, which allowed us to bias stimuli such that they are processed predominantly by the intact ventral visual pathway. Our findings reveal that the impairment in global processing that characterizes simultanagnosia stems from a disruption in the processing of low-spatial frequencies through the dorsal pathway. These findings advance our understanding of the relationship between visuospatial attention and perception and reveal the neural mechanism mediating the disposition to see the 'forest before the trees'.

Diagnosis of recanalization of the intracranial artery has poor inter-rater reliability

BACKGROUND AND PURPOSE

Recanalization is the important outcome measure for acute stroke therapy. Several methods of recanalization assessment are used in clinical practice, but few studies have addressed their reliability. We, therefore, sought to assess interobserver reliability of the diagnosis of intracranial artery recanalization following intervention by using TIMI criteria.

MATERIALS AND METHODS

The digital angiography scans of all patients with acute ischemic stroke during 2009 undergoing DSA and endovascular procedures at Ostrava University Hospital were assessed in the study. Images were retrospectively evaluated for intracranial artery recanalization on the TIMI scale by 2 experienced neuroradiologists who were blinded to clinical findings and to each other.

RESULTS

The angiography scans of 43 patients (16 females; age, 70.5 ± 14 years; median baseline NIHSS score, 15 [IQR, 11-18]) were retrospectively evaluated in our study. At 3 months, 27% of patients had mRS scores ≤ 2 and mortality was 18%. Two radiologists diagnosed TIMI grades as follows: TIMI 0, 16%, and 16%; TIMI 1, 21%, and 8%; TIMI 2a, 32% and 29%; TIMI 2b, 13% and 16%; TIMI 3, 18, and 31%. Interobserver agreement for recanalization was weighted κ = 0.4 (95% CI, 0.2-0.6).

CONCLUSIONS

The diagnosis of recanalization after interventional procedures was found to have poor interobserver agreement between 2 experienced neuroradiologists. TIMI criteria, therefore, do not permit reliable comparison of the efficacy of recanalization therapy among different studies.

Tolerability and safety of perampanel: two randomized dose-escalation studies

OBJECTIVES

To evaluate, for the first time in patients with epilepsy, the tolerability and safety of escalating doses of oral perampanel, a novel, selective, non-competitive AMPA antagonist, as adjunctive therapy for refractory partial-onset seizures.

MATERIALS AND METHODS

Two consecutive, randomized, double-blind, dose-escalation studies recruited adults (18-70 years) with uncontrolled partial-onset seizures receiving one to three concomitant antiepileptic drugs. In study 206, patients were treated for 12 weeks (8-week dose-titration, 4-week dose-maintenance) with placebo or perampanel (up to 4 mg/day, dosed once- or twice-daily). In study 208, patients received placebo or perampanel once-daily (up to 12 mg) for 16 weeks (12-week titration, 4-week maintenance).

RESULTS

Overall, 153 patients were randomized into study 206 (perampanel twice-daily, n = 51; perampanel once-daily, n = 51; placebo, n = 51). Study 208 included 48 patients (perampanel once-daily, n = 38; placebo, n = 10). The highest dose in study 206 - 4 mg/day - was well tolerated, with similar proportions of patients tolerating once-daily (82.4%) and twice-daily (82.4%) perampanel and placebo (82.4%) treatments. In study 208 most patients tolerated doses of ≥ 6 mg perampanel once-daily in a Kaplan-Meier analysis. In both studies, the most common adverse events were CNS-related; most were of mild/moderate severity.

CONCLUSIONS

Perampanel was well tolerated across doses of 4-12 mg/day. The studies showed preliminary evidence of efficacy and identified doses to be evaluated in larger clinical studies.

Emotional valence modulates the preference for curved objects

Previous studies have shown that people prefer objects with curved contours over objects with sharp contours. However, those studies used stimuli that were mainly neutral in emotional valence. We tested here the interplay between visual features and general valence as positive or negative. After replicating curvature preferences for neutral objects, we used positive (cake, chocolate) and negative (snake, bomb) stimuli to examine if emotional valence-through response prioritisation-modulates the preference for curved objects. We found that people indeed preferred the curved versions of objects to the sharp versions of the same objects, but only if the objects were neutral or positive in emotional valence. There were no difference in liking for objects with negative emotional valence. This is evidence that the aesthetic response is adaptive, in this case prioritising valence over contour as demanded by the general semantic classification.

Preference for symmetry: only on mars?

Preference for symmetry is a robust bias found throughout the animal kingdom. In humans, the bias for symmetry has been documented in numerous domains, including faces and visual patterns. The function of this potent aesthetic bias still eludes us, but prominent accounts focus on its role in mate selection and perceptual fluency. Previous studies have shown that both males and females find symmetrical faces to be more attractive, but here we show that the preference for symmetry in neutral stimuli (ie everyday and meaningless visual objects) is, on the other hand, unique to male participants. Our findings indicate that symmetry preference cannot be explained exclusively by perceptual or computational efficiency, because such an account is domain-independent yet females did not show any bias for the objects tested here. Further studies are needed to elucidate the utility of the male preference for visual object symmetry.

Wait for the second marshmallow? Future-oriented thinking and delayed reward discounting in the brain

Humans tend to discount the value of delayed rewards. Peters and Büchel show in this issue of Neuron that the ability to appraise the value of such future rewards improves when future-oriented cognitive processes are recruited using personally relevant information. These results provide the platform for exciting new questions.