Mikhail Votinov

The dynorphin/κ-opioid receptor (KOP-R) system has been shown to play a role in different types of behavior regulation, including reward-related behavior and drug craving. It has been shown that alleles with 3 or 4 repeats (HH genotype) of the variable nucleotide tandem repeat (68-bp VNTR) functional polymorphism of the prodynorphin (PDYN) gene are associated with higher levels of dynorphin peptides than alleles with 1 or 2 repeats (LL genotype). We used fMRI on N = 71 prescreened healthy participants to investigate the effect of this polymorphism on cerebral activation in the limbic-corticostriatal loop during reward anticipation. Individuals with the HH genotype showed higher activation than those with the LL genotype in the medial orbitofrontal cortex (mOFC) when anticipating a possible monetary reward. In addition, the HH genotype showed stronger functional coupling (as assessed by effective connectivity analyses) of mOFC with VMPFC, subgenual anterior cingulate cortex, and ventral striatum during reward anticipation. This hints at a larger sensitivity for upcoming rewards in individuals with the HH genotype, resulting in a higher motivation to attain these rewards. These findings provide first evidence in humans that the PDYN polymorphism modulates neural processes associated with the anticipation of rewards, which ultimately may help to explain differences between genotypes with respect to addiction and drug abuse.

Localization of sound sources is critical for an appropriate behavioral response. This is not only true for localization in the horizontal plane but also for localization in depth. Depth ranging of sound sources implicates various distance cues, among others sound intensity. In this study, we measured human electroencephalography and compared mismatch negativity (MMN) amplitudes and latencies for horizontal motion, radial motion, and pure intensity changes in the free field. We observed similar MMN latencies for horizontal and radial motion, whereas MMN responses to pure intensity changes were comparably delayed. MMN amplitudes and latencies were not different for approaching and receding sounds. Our data suggest similar fast processing for horizontal and radial motion, whereas pure intensity changes are possibly processed with less priority.

Ranging of auditory objects relies on several acoustic cues and is possibly modulated by additional visual information. Sound pressure level can serve as a cue for distance perception because it decreases with increasing distance. In this agnetoencephalography (MEG) experiment, we tested whether psychophysical loudness judgment and N1m MEG responses are modulated by visual distance cues. To this end, we paired noise bursts at different sound pressure levels with synchronous visual cues at different distances. We hypothesized that noise bursts paired with far visual cues will be perceived louder and result in increased N1m amplitudes compared to a pairing with close visual cues. The rationale behind this was that listeners might compensate the visually induced object distance when processing loudness. Psychophysically, we observed no significant modulation of loudness judgments by visual cues. However, N1m MEG responses at about 100 ms after stimulus onset were significantly stronger for far versus close visual cues in the left auditory cortex. N1m responses in the right auditory cortex increased with increasing sound pressure level, but were not modulated by visual distance cues. Thus, our results suggest an audio-visual interaction in the left auditory cortex that is possibly related to cue integration for auditory distance processing.