Asymmetry of automatic change detection shown by the visual mismatch negativity: An additional feature is identified faster than missing features

In two experiments, we demonstrated that an asymmetric effect of the brain electric activity that is elicited by nonattended visual stimuli is similar to the one found in responses observed in the performance of visual search tasks. The automatic detection of violated sequential regularities was investigated by measuring the visual mismatch negativity (vMMN) component of event-related brain potentials (ERPs). In Experiment 1, within a sequence of stimulus displays with O characters, infrequently presented Q characters elicited an earlier vMMN than did infrequent O characters within a sequence of Q characters. In Experiment 2, similar asymmetric results emerged if only 16 % of the characters were different within an infrequent display. In both experiments, these stimuli were irrelevant; during the stimulus sequences, participants performed a demanding videogame. We suggest that the underlying match/mismatch and decision processes are similar in the vMMN and in the attention-related visual search paradigm, at least in the case of the stimuli in the present experiments

Mismatch negativity does not show evidence of memory reactivation in the visual modality

The possibility of reactivation of the memory representation underlying visual mismatch negativity (vMMN) was investigated in a modified passive roving-standard paradigm. Stimuli (arrays of Gábor patches) were presented in sequences with blank interval between the sequences. The first member of each sequence was identical to the standard of the previous sequence, while the second stimulus had different orientation therefore the second stimulus was considered as deviant. In a control condition the stimuli of the previous sequence had random orientations. Event-related potentials (ERPs) in response to the deviants were compared to ERPs in response to the (physically identical) second stimulus of the control sequences. The comparison showed emergence of a positive component at an early (98-132 ms) latency range elicited by deviants. This component is interpreted as an index of increased sensitivity to rare changes in sequences dominated by identical stimuli rather than a component specific to violation of sequential regularity. Consequently, contrary to the findings in the auditory modality, the first stimulus of the sequence did not reactivate the memory representation underlying the vMMN, since subsequent deviant elicited no vMMN

Elemi szabályosságok reprezentációja a látásban: Pszichofiziológiai vizsgálatok = Representation of elementary rules in vision: Psychophysiological investigations

Fő célunk a vizuális automatikus emlékezeti rendszer sajátságainak vizsgálata volt a vizuális eltérési negativitás eseményhez (EN) kötött potenciál összetevő elemzésével. Mivel az eltérési negativitás annak jele, ha egy esemény megszegi az ingersorozat szabályszerűségeit, jelentkezése rámutat arra, ha az emlékezeti regisztrálta a szabályszerűséget. Eredményeink szerint az emlékezeti rendszer nem egyedi vizuális sajátságokat tárol, hanem eseményeket, azaz egy objektum több sajátságának egyidejű változása nem növeli az eltérő negativitást. Additív hatás mutatkozik viszont, ha egyidejűleg több esemény változik. Az aktuálsi viselkedés és az automatikus változás detekciója nem független: a feladat azonos típusú változások esetén az eltérési negativitás csökken. Eltérően a hallás hasonló rendszeréhet, a vizuális rendszer nem érzékeny hosszabb tartamú emlékezeti reaktivációs hatásaira. Valódi és látszólagos eltérések hasonló EN hatásokkal járnak. A rendszer képes perceptuális és érzelmi kategóriák (horizontális szimmetria) regisztrációjára, viszont nem jön létre EN, ha az események sorozatából nem jön létre szabályszerűség reprezentációja. Mivel az emlékezeti rendszer képes feltételes szabályszerűségek tárolására, így valószínűsíthető, hogy a vizuális észlelésben prediktív funkcióval rendelkezik. | As the main purpose of the project was the investigation of the characteristics of an implicit visual memory system. The method was the analysis of the visual mismatch negativity (vMMN) event-related potential component. VMMN emerges whenever an event violates the regularity of stimulus sequences, therefore vMMN appearance is an indicator of registered regularity. As our results show, beyond the registration of individual visual features, the system is capable of storing deviant events, i.e., vMMN to event with simultaneous deviant features does not elicit increased vMMN. However, simultaneous deviancy of two events elicits additive vMMN. VMMN is not independent of the task-related stimuli. Irrelevant stimuli shearing the characteristics of task-relevant ones elicit vMMN with decreased amplitude. Contrary to the homolog auditory memory, the system underlying vMMN is insensitive to long-term memory effects (reactivation). Real and apparent (illusory) deviancies elicit similar vMMN. The system is capable of registering perceptual (horizontal symmetry) and emotional categories. However, without the acquisition of category, no vMMN emerges. The system is sensitive to conditional regularities; therefore it is possible that it has a predictive function in visual perceptio

Hemokinin-1 is a mediator of chronic restraint stress-induced pain

The Tac4 gene-derived hemokinin-1 (HK-1) binds to the NK1 receptor, similarly to Substance P, and plays a role in acute stress reactions and pain transmission in mice. Here we investigated Tac4 mRNA expression in stress and pain-related regions and its involvement in chronic restraint stress-evoked behavioral changes and pain using Tac4 gene-deleted (Tac4-/-) mice compared to C57Bl/6 wildtypes (WT). Tac4 mRNA was detected by in situ hybridization RNAscope technique. Touch sensitivity was assessed by esthesiometry, cold tolerance by paw withdrawal latency from 0°C water. Anxiety was evaluated in the light-dark box (LDB) and open field test (OFT), depression-like behavior in the tail suspension test (TST). Adrenal and thymus weights were measured at the end of the experiment. We found abundant Tac4 expression in the hypothalamic-pituitary-adrenal axis, but Tac4 mRNA was also detected in the hippocampus, amygdala, somatosensory and piriform cortices in mice, and in the frontal regions and the amygdala in humans. In Tac4-/- mice of both sexes, stress-induced mechanical, but not cold hyperalgesia was significantly decreased compared to WTs. Stress-induced behavioral alterations were mild or absent in male WT animals, while significant changes of these parameters could be detected in females. Thymus weight decrease can be observed in both sexes. Higher baseline anxiety and depression-like behaviors were detected in male but not in female HK-1-deficient mice, highlighting the importance of investigating both sexes in preclinical studies. We provided the first evidence for the potent nociceptive and stress regulating effects of HK-1 in chronic restraint stress paradigm. Identification of its targets might open new perspectives for therapy of stress-induced pain

Single-Molecule Imaging Reveals Rapid Estradiol Action on the Surface Movement of AMPA Receptors in Live Neurons

Gonadal steroid 17β-estradiol (E2) exerts rapid, non-genomic effects on neurons and strictly regulates learning and memory through altering glutamatergic neurotransmission and synaptic plasticity. However, its non-genomic effects on AMPARs are not well understood. Here, we analyzed the rapid effect of E2 on AMPARs using single-molecule tracking and super-resolution imaging techniques. We found that E2 rapidly decreased the surface movement of AMPAR via membrane G protein-coupled estrogen receptor 1 (GPER1) in neurites in a dose-dependent manner. The cortical actin network played a pivotal role in the GPER1 mediated effects of E2 on the surface mobility of AMPAR. E2 also decreased the surface movement of AMPAR both in synaptic and extrasynaptic regions on neurites and increased the synaptic dwell time of AMPARs. Our results provide evidence for understanding E2 action on neuronal plasticity and glutamatergic neurotransmission at the molecular level