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Until now, melanopsin (OPN4) - a specialized photopigment being responsive especially to blue light wavelengths - has not been found in the human brain at protein level outside the retina. More specifically, OPN4 has only been found in about 2% of retinal ganglion cells (i.e. in intrinsically photosensitive retinal ganglion cells), and in a subtype of retinal cone-cells. Given that Allen Institute for Brain Science has described a wide distribution of OPN4 mRNA in two human brains, we aimed to investigate whether OPN4 is present in the human brain also at protein level. Western blotting and immunohistochemistry, as well as immunoelectron microscopy, were used to analyse the existence and distribution of OPN4 protein in 18 investigated areas of the human brain in samples obtained in forensic autopsies from 10 male subjects (54 ± 3.5 years). OPN4 protein expression was found in all subjects, and, furthermore, in 5 out of 10 subjects in all investigated brain areas localized in membranous compartments and cytoplasmic vesicles of neurons. To our opinion, the wide distribution of OPN4 in central areas of the human brain evokes a question whether ambient light has important straight targets in the human brain outside the retinohypothalamic tract (RHT). Further studies are, however, needed to investigate the putative physiological phototransductive actions of inborn OPN4 protein outside the RHT in the human brain.

Seasonal affective disorder (SAD) is a subtype of recurrent unipolar or bipolar depressive disorder with a higher prevalence in winter than in summer. The biological underpinnings of SAD are so far poorly understood. Studies examining SAD have found disturbances between the molecular and connectivity scales. The aim of the study was to explore changes in functional connectivity typical for SAD.We investigated unmedicated, untreated SAD patients and healthy controls using resting-state functional magnetic resonance imaging (rs-fMRI) utilizing graph theory, a data driven and hypothesis free approach, to model functional networks of the brain.Comparing whole brain network properties using graph theory we observed globally affected network topologies with increasing pathlength in SAD. Nodal changes, however, were highly restricted to bilateral inferior occipital cortex. Interestingly, we found a lateralization where hyper-connectedness was restricted to right inferior occipital cortex and hyper-efficiency was found in the left inferior occipital cortex. Furthermore, we found these nodes became more "hub like" in patients, suggesting a greater functional role.Our work stresses the importance of abnormal intrinsic processing during rest, primarily affecting visual areas and subsequently changing whole brain networks, and thus providing an important hint towards potential future therapeutic approaches.

The autonomic nervous system and circulating hormones control a stress reaction through a complex interaction. We tested the hypothesis that changes in cardiac vagal regulation may be positively associated with the serum testosterone-to-cortisol ratio during the first week of military service in 24 conscripts aged 19.0±0.3 years. Cardiac autonomic function was assessed by measuring high-frequency (HF: 0.15–0.4 Hz) and low-frequency (LF: 0.04–0.15 Hz) power spectral indices of R-R intervals during supine rest and during a controlled standing condition (5 min for both) from the second to the seventh mornings at the beginning of military service. Blood samples were collected to analyse the basal serum testosterone-to-cortisol ratio on the seventh morning. Changes in heart rate and high-frequency power measured in the standing condition were positively correlated with the serum testosterone-to-cortisol ratio at day 7 (r= − 0.42 and r=0.45, respectively; P