"Mickey Mousing" in the Brain: Motion-Sound Synesthesia and the Subcortical Substrate of Audio-Visual Integration.

Motion-sound synesthesia is characterized by illusory auditory sensations linked to the pattern and rhythms of motion (dubbed "Mickey Mousing" as in cinema) of visually experienced but soundless object, like an optical flow array, a ball bouncing or a horse galloping. In an MRI study with a group of three synesthetes and a group of eighteen control participants, we found structural changes in the brains of synesthetes in the subcortical multisensory areas of the superior and inferior colliculi. In addition, functional magnetic resonance imaging data showed activity in motion-sensitive regions, as well as temporal and occipital areas, and the cerebellum. However, the synesthetes had a higher activation within the left and right cuneus, with stronger activations when viewing optical flow stimuli. There was also a general difference in connectivity of the colliculi with the above mentioned regions between the two groups. These findings implicate low-level mechanisms within the human neuroaxis as a substrate for local connectivity and cross activity between perceptual processes that are "distant" in terms of cortical topography. The present findings underline the importance of considering the role of subcortical systems and their connectivity to multimodal regions of the cortex and they strengthen a parsimonious account of synesthesia, at the least of the visual-auditory type.

Acetaminophen use during pregnancy and offspring attention deficit hyperactivity disorder - a longitudinal sibling control study.

Background: Maternal acetaminophen use during pregnancy is associated with increased risk of ADHD in the child. This could reflect causal influence of acetaminophen on fetal neurodevelopment or could be due to confounding factors. The aim of the current study was to examine unmeasured familial confounding factors of this association. Methods: We used data from 26,613 children from 12,902 families participating in the prospective Norwegian Mother, Father, and Child Cohort Study (MoBa). The MoBa was linked to the Norwegian Medical Birth Register and the Norwegian Patient Registry. Siblings discordant for prenatal acetaminophen exposure were compared regarding risk of having an ADHD diagnosis. Results: Children exposed to acetaminophen up to 28 days during pregnancy did not have increased risk of receiving an ADHD diagnosis compared to unexposed children. The adjusted Hazard ratio (aHR) was 0.87 (95% C.I. = 0.70-1.08) for exposure 1 to 7 days, and 1.13 (95% C.I. = 0.82-1.49) for 8-28 days. Long-term exposure (29 days or more) was associated with a two-fold increase in risk of ADHD diagnosis (aHR = 2.02, 95% C.I = 1.17-3.25). In the sibling control model, the association between long-term acetaminophen use and ADHD in the child was aHR = 2.77 (95% C.I. = 1.48-5.05) at the between-family level, and aHR = 1.06 (95% C.I. = 0.51-2.05) at the within-family level. Conclusions: Both the exposed and the unexposed children of mothers with long-term use of acetaminophen in one of the pregnancies had increased risk of receiving an ADHD diagnosis. This indicates that the observed association between long-term acetaminophen use during pregnancy and ADHD in the child may at least partly be confounded by unobserved family factors.

Multiple object tracking and pupillometry reveal deficits in both selective and intensive attention in unilateral spatial neglect.

INTRODUCTION: Unilateral spatial neglect is typically associated with a spatial attention deficit, as neglect patients fail to respond to objects in their contralesional hemispace. However, growing evidence suggests that also nonspatial attention impairments (e.g., arousal) play a role and influences the recovery from this syndrome. METHOD: Nonspatial and spatial attentional functions were assessed in 13 right-hemisphere stroke patients with neglect, 13 right-hemisphere stroke patients without neglect, and 26 healthy control participants, by investigating pupillary responses and performance on a multiple object tracking task (MOT)-that is, a dynamic task of divided attention where cognitive load can be manipulated precisely. The task was alternately presented in the left and right hemispace to assess spatial attention functioning. RESULTS: Results revealed smaller pupillary dilations in both patient groups than in controls, suggesting reduced attentional resources or arousal, and while patients without neglect and controls revealed significant effects of cognitive load on their pupillary responses, neglect patients did not. Both MOT and visual search (VS) tasks revealed spatial symptoms of neglect, while MOT performance measures additionally indicated reduced cognitive functioning in the ipsilateral hemispace. Moreover, the MOT task revealed severely reduced divided attention in neglect patients, as they only managed to track one target in the contralesional hemispace and occasionally two targets at the time in the ipsilesional hemispace. CONCLUSION: Our results suggest that a stroke may lead to reduced attentional resources. Furthermore, as neglect patients showed no indications in their pupillary responses that they were able to regulate the allocation of resources in accordance with the varying task demands, it appears they additionally had impaired mechanisms for adjusting arousal levels. Our findings suggest that neglect involves nonspatial as well as spatial attention impairments, as also ipsilesional performance was reduced in this group.

Binocular rivalry after right-hemisphere stroke: Effects of attention impairment on perceptual dominance patterns.

Binocular rivalry is when perception fluctuates while the stimuli, consisting of different images presented to each eye, remain unchanged. The fluctuation rate and predominance ratio of these images are regarded as information source for understanding properties of consciousness and perception. We administered a binocular rivalry task to 26 right-hemisphere stroke patients and 26 healthy control participants, using stimuli such as simple Gabor anaglyphs. Each single Gabor image was of unequal spatial frequency compared to its counterpart, allowing assessment of the effect of relative spatial frequency on rivalry predominance. Results revealed that patients had significantly decreased alternation rate compared to healthy controls, with severity of patients' attention impairment predicting alternation rates. The patient group had higher predominance ratio for high compared to low relative spatial frequency stimuli consistent with the hypothesis that damage to the right hemisphere may disrupt processing of relatively low spatial frequencies. Degree of attention impairment also predicted the effect of relative spatial frequencies. Lastly, both groups showed increased predominance rates in the right eye compared to the left eye. This right eye dominance was more pronounced in patients than controls, suggesting that right hemisphere stroke may additionally affect eye predominance ratios.

Bridging the gap between clinical neuroscience and cognitive rehabilitation: the role of cognitive training, models of neuroplasticity and advanced neuroimaging in future brain injury rehabilitation.

BACKGROUND: Magnetic resonance imaging (MRI) has brought about advances in the fields of brain plasticity and lifespan brain change, that might be of special interest for cognitive rehabilitation research and, eventually, in clinical practice. Parallel, intensive cognitive training studies show promising results for the prospect of retraining some of the impaired functioning following acquired brain injury. OBJECTIVES: However, cognitive training research is largely performed without concurrent assessments of brain structural change and reorganization, which could have addressed possible mechanisms of training-related neuroplasticity. METHODS: Criticism of cognitive training studies is often focused on lack of ecologically valid, daily-living assessments of treatment effect, and on whether the applied cognitive measures overlap too much with the training exercises. Yet, the present paper takes another point of view, where the relevance of recent MRI research of brain plasticity to the field of cognitive rehabilitation is examined. RESULTS: Arguably, treatment ought to be measured at the same level of the International Classification of Functioning, Disability and Health model, as it is targeting. In the case of cognitive training that will be the "body structure" and "body function" levels. CONCLUSIONS: MRI has shown promise to detect macro- and microstructural activity-related changes in the brain following intensive training.