Division of Neuroscience and Experimental Psychology

The feedback-related negativity, a frontocentral event-related potential (ERP) occurring 200-350 milliseconds (ms) after emotionally-valued outcomes, has been posited as the neural correlate of reward prediction error, a key component of associative learning. Recent evidence challenged this interpretation and has led to the suggestion that this ERP expresses salience, instead. Here we distinguish between utility prediction error and salience by delivering or withholding hedonistically matched appetitive and aversive tastes, and measure ERPs to cues signalling each taste. We observed a typical FRN (computed as the loss-minus-gain difference wave) to appetitive taste, but a reverse-FRN to aversive taste. When tested axiomatically, frontocentral ERPs showed a salience response across tastes, with a particularly early response to outcome delivery, supporting recent propositions of a fast, unsigned and unspecific response to salient stimuli. ERPs also expressed aversive prediction error
peaking at 285ms, which conformed to the logic of an axiomatic model of prediction error. With stimuli that most resemble those used in animal models we did not detect any frontocentral ERP signal for utility prediction error, in contrast with dominant views of the functional role of the feedback-related negativity ERP. We link the animal and human literature and present a challenge for current perspectives on associative learning research using ERPs.

Background: Pain is modulated by expectation. Event-related potential (ERP) studies of the influence of expectation on pain typically utilise laser heat stimulation to provide a controllable nociceptive-specific stimulus. Short painful electric stimulation has a number of practical advantages, but is less nociceptive-specific. We compared the modulation of electric versus laser-evoked pain by expectation, and their corresponding pain-evoked and anticipatory ERPs. New Method: We developed understanding of recognised methods of laser and electric stimulation. We tested whether pain perception and neural activity induced by electric stimulation was modulated by expectation, whether this expectation elicited anticipatory neural correlates, and how these measures compared to those associated with laser stimulation. We elicited cue-evoked expectations of high and low pain and compared subjective ratings and corresponding ERPs in response to the delivery of laser and electric stimulation in a within-participant design. Results: Despite sensory and affective differences between laser and electric pain, intensity ratings and pain-evoked potentials were modulated equivalently by expectation, though ERPs only correlated with pain ratings in the laser pain condition. Anticipatory correlates significantly differentiated pain intensity expectation to laser but not electric pain. Comparison with Existing Method: Previous studies have consistently shown that laser-evoked potentials are modulated by expectation. We extend this by showing electric pain-evoked potentials are equally modulated by expectation, within the same participants. We also show a difference between the pain types in anticipation. Conclusions: Though laser-evoked potentials express a stronger relationship with pain perception, both laser and electric stimulation may be used to study the modulation of pain-evoked potentials by expectation. Anticipatory-evoked potentials are elicited by both pain types, but they may reflect different processes and did not correlate with pain perception.

Somatotopic reorganization of primary motor cortex (M1) has been described in several neurological conditions associated with chronic pain. We hypothesized that such reorganization impacts on the mechanisms of M1 stimulation induced analgesia and may either compromise the treatment effect of or provide an alternative target site for repetitive transcranial magnetic stimulation (rTMS). The aim of the study was to compare pain relief following rTMS of the standard motor "hotspot" with that of the reorganized area. We used TMS motor mapping in 30 patients to establish the location of the standard motor "hotspot" (site A) and an alternative site located in the reorganized area (site B), both within M1. Where TMS mapping was not possible (N = 8) we determined the location of the two sites using task-related fMRI. We compared the analgesic effect on neuropathic pain of 5 sessions of navigated rTMS applied over (i) site A, (ii) site B, and (iii) occipital fissure (SHAM ...

Perception is the result of both expectation and sensory stimulation. This is reflected in placebo analgesia, where expecting low pain leads a painful stimulus to feel less painful. Yet it is maladaptive for a highly erroneous expectation to result in an unrealistically low pain experience. We hypothesised that in estimating the intensity of a painful stimulus which is preceded by a very discrepant expectation, the perception is influenced less by the expectation. We modelled the reported pain intensity as a function of the prediction error. We used linear mixed modelling on two independently collected pain cueing datasets, the second of which was preregistered (osf.io/5r6z7). Reported pain intensities were best explained by a quartic polynomial model of the prediction error, indicating the influence of expectations on perceived pain decreased when pain was highly discrepant to expectation, suggesting that the size of prediction error has a functional role in pain perception.

HIV enters the nervous system in the first hours of infection and persists throughout the infection. Neuropsychological symptoms are seen in HIV-infected patients and these are usually the first signs of the disease. In addition to memory and executive functions, these patients also have changes in mental activity, impaired perception, and decreased level of consciousness. In addition to the immune system, HIV affects the nervous system and brain and produces neurological sequelae, often causing forgetfulness and cognitive problems (Vance, Fazeli, Moneyham, Keltner and Raper, 2013).

In this research, it is aimed to evaluate the frontal area in HIV patients in detail through neuropsychological tests. Neuropsychological test battery to assess cognitive changes caused by HIV infection in HIV-infected patients; WCST, Stroop Test, Trail Making Test, Digit Span Test, Clock Drawing Test, Boston Naming Test, Cube Design Test, California Test and Hamilton Depression Rating Scale were applied. 43 volunteer patients diagnosed with HIV, aged between 18 and over, were included in the study. EEG and MRI results of the patients taken in the last 6 months were examined, and patients with lesions and patients with severe depression were excluded from the study. The study included criteria such as educational status, initial CD4 + T lymphocyte cell count, and duration of illness. When the relationship between the CD4 + groups on neuropsychological test scores, education levels and depression scores was examined, the analysis results of the CD4 + groups according to Hamilton test scores and California subtest scores were found to be statistically significant. There was no significant relationship between the duration of illness and test scores. Correlation analysis was not found significant according to the neuropsychological test scores of the Hamilton test. At the same time, no statistically significant difference was found between CD4 + groups according to education levels.