Tina Weis

Effects of L-dopa during auditory instrumental learning in humans.

The dopaminergic neurotransmitter system is critically involved in promoting plasticity in auditory cortex. We combined functional magnetic resonance imaging (fMRI) and a pharmacological manipulation to investigate dopaminergic modulation of neural activity in auditory cortex during instrumental learning. Volunteers either received 100 mg L-dopa (Madopar) or placebo in an appetitive, differential instrumental conditioning paradigm, which involved learning that a specific category of frequency modulated tones predicts a monetary reward when fast responses were made in a subsequent reaction time task. The other category of frequency modulated tones was not related to a reward. Our behavioral data provides evidence that dopaminergic stimulation differentially impacts on the speed of instrumental responding in rewarded and unrewarded trials. L-dopa increased neural BOLD activity in left auditory cortex to tones in rewarded and unrewarded trials. This increase was related to plasma L-dopa levels and learning rate. Our data thus provides evidence for dopaminergic modulation of neural activity in auditory cortex, which occurs for both auditory stimuli related to a later reward and those not related to a reward.

Feedback that confirms reward expectation triggers auditory cortex activity

Associative learning studies have shown that the anticipation of reward and punishment shapes the representation of sensory stimuli, which is further modulated by dopamine. Less is known about whether and how reward delivery activates sensory cortices and the role of dopamine at that time point of learning. We used an appetitive instrumental learning task in which participants had to learn that a specific class of frequency-modulated tones predicted a monetary reward following fast and correct responses in a succeeding reaction time task. These fMRI data were previously analyzed regarding the effect of reward anticipation, but here we focused on neural activity to the reward outcome relative to the reward expectation and tested whether such activation in the reward reception phase is modulated by L-DOPA. We analyzed neural responses at the time point of reward outcome under three different conditions: 1) when a reward was expected and received, 2) when a reward was expected but not received, and 3) when a reward was not expected and not received. Neural activity in auditory cortex was enhanced during feedback delivery either when an expected reward was received or when the expectation of obtaining no reward was correct. This differential neural activity in auditory cortex was only seen in subjects who learned the reward association and not under dopaminergic modulation. Our data provide evidence that auditory cortices are active at the time point of reward outcome. However, responses are not dependent on the reward itself but on whether the outcome confirmed the subjects expectations.

Assessment of aversive stimuli dependent attentional binding by the N170 VEP component

For social species nonverbal communication by assessment of emotion expression is crucial for building up and maintaining social structures. In humans, body language not only includes gestures but also a variety of facial expressions. Negative associated facial expressions, e.g. disgust, fear, anger call for a higher attentional binding due their evolutionary background, denoting directly personal dangers for the receptive individual. In a number of psychiatric disorders such as schizophrenia or autism spectrum diseases, the assessment of emotions in faces is disturbed, leading to even more pronounced social cuts. In this article we present a new methodology for monitoring the attentional binding to emotion–tinged stimuli in a face recognition task. We were able to demonstrate a significant difference in habituation behavior to neutral and negative associated faces respectively. In future, this methodology might provide a fast and reliable scheme for the detection of psychiatric disorders comprising dysfunction of limbic structures.

When speech enhances Spatial Musical Association of Response Codes: Joint spatial associations of pitch and timbre in nonmusicians

Previous studies have shown that the effect of the Spatial Musical Association of Response Codes (SMARC) depends on various features, such as task conditions (whether pitch height is implicit or explicit), response dimension (horizontal vs. vertical), presence or absence of a reference tone, and former musical training of the participants. In the present study, we investigated the effects of pitch range and timbre: in particular, how timbre (piano vs. vocal) contributes to the horizontal and vertical SMARC effect in nonmusicians under varied pitch range conditions. Nonmusicians performed a timbre judgement task in which the pitch range was either small (6 or 8 semitone steps) or large (9 or 12 semitone steps) in a horizontal and a vertical response setting. For piano sounds, SMARC effects were observed in all conditions. For the vocal sounds, in contrast, SMARC effects depended on pitch range. We concluded that the occurrence of the SMARC effect, especially in horizontal response settings, depends on the interaction of the timbre (vocal and piano) and pitch range if vocal and instrumental sounds are combined in one experiment: the human voice enhances the attention, both to the vocal and the instrumental sounds.

SNARC (spatial–numerical association of response codes) meets SPARC (spatial–pitch association of response codes): Automaticity and interdependency in compatibility effects

Concepts, including the mental number line, or addressing pitch as high and low, suggest that the spatial–numerical and spatial–pitch association of response codes (SNARC and SPARC) effects are domain-specific and thus independent. Alternatively, there may be dependencies between these effects, because they share common automatic or controlled decision mechanisms. In two experiments, participants were presented with spoken numbers in different pitches; their numerical value, pitch, and response compatibility were varied systematically. This allowed us to study SNARC and SPARC effects in a factorial design (see also Fischer, Riello, Giordano, & Rusconi, 2013). Participants judged the stimuli on numerical magnitude, pitch, or parity (odd–even). In all tasks, the SNARC and SPARC effects had superadditive interactions. These were interpreted as both effects sharing a common mechanism. The task variation probes the mechanism: In the magnitude judgement task, numerical magnitude was explicit, whereas pitch was implicit; in the pitch judgement task, it was vice versa. In the parity judgement task, both dimensions were implicit. Regardless of whether they were implicit or explicit, both SNARC and SPARC effects occurred in all tasks. We concluded that by not requiring focal attention the common mechanism operates automatically.

Positive and negative reinforcement activate human auditory cortex

Prior studies suggest that reward modulates neural activity in sensory cortices, but less is known about punishment. We used functional magnetic resonance imaging and an auditory discrimination task, where participants had to judge the duration of frequency modulated tones. In one session correct performance resulted in financial gains at the end of the trial, in a second session incorrect performance resulted in financial loss. Incorrect performance in the rewarded as well as correct performance in the punishment condition resulted in a neutral outcome. The size of gains and losses was either low or high (10 or 50 Euro cent) depending on the direction of frequency modulation. We analyzed neural activity at the end of the trial, during reinforcement, and found increased neural activity in auditory cortex when gaining a financial reward as compared to gaining no reward and when avoiding financial loss as compared to receiving a financial loss. This was independent on the size of gains and losses. A similar pattern of neural activity for both gaining a reward and avoiding a loss was also seen in right middle temporal gyrus, bilateral insula and pre-supplemental motor area, here however neural activity was lower after correct responses compared to incorrect responses. To summarize, this study shows that the activation of sensory cortices, as previously shown for gaining a reward is also seen during avoiding a loss.

Attention allows the SNARC effect to operate on multiple number lines

To investigate whether participants can activate only one spatially oriented number line at a time or multiple number lines simultaneously, they were asked to solve a unit magnitude comparison task (unit smaller/larger than 5) and a parity judgment task (even/odd) on two-digit numbers. In both these primary tasks, decades were irrelevant. After some of the primary task trials (randomly), participants were asked to additionally solve a secondary task based on the previously presented number. In Experiment 1, they had to decide whether the two-digit number presented for the primary task was larger or smaller than 50. Thus, for the secondary task decades were relevant. In contrast, in Experiment 2, the secondary task was a color judgment task, which means decades were irrelevant. In Experiment 1, decades’ and units’ magnitudes influenced the spatial association of numbers separately. In contrast, in Experiment 2, only the units were spatially associated with magnitude. It was concluded that multiple number lines (one for units and one for decades) can be activated if attention is focused on multiple, separate magnitude attributes.

There’s a SNARC in the Size Congruity Task

The size congruity effect involves interference between numerical magnitude and physical size of visually presented numbers: congruent numbers (either both small or both large in numerical magnitude and physical size) are responded to faster than incongruent ones (small numerical magnitude/large physical size or vice versa). Besides, numerical magnitude is associated with lateralized response codes, leading to the Spatial Numerical Association of Response Codes (SNARC) effect: small numerical magnitudes are preferably responded to on the left side and large ones on the right side. Whereas size congruity effects are ascribed to interference between stimulus dimensions in the decision stage, SNARC effects are understood as (in)compatibilities in stimulus-response combinations. Accordingly, size congruity and SNARC effects were previously found to be independent in parity and in physical size judgment tasks. We investigated their dependency in numerical magnitude judgment tasks. We obtained independent size congruity and SNARC effects in these tasks and replicated this observation for the parity judgment task. The results confirm and extend the notion that size congruity and SNARC effects operate in different representational spaces. We discuss possible implications for number representation.

Is it still speech? Different processing strategies in learning to discriminate stimuli in the transition from speech to non-speech including feedback evaluation

HIGHLIGHTSPerformance feedback was given for discrimination of blended speech (vowels) and non‐speech (spectral rotated vowels) stimuli.Two groups of participants were identified, good and poor performers.For auditory stimulation, good performers showed neural activation in the ventral auditory pathway, including the primary auditory cortex and the anterior superior temporal sulcus.Poor performers showed neural activation in the dorsal auditory pathway, including the bilateral superior temporal gyrus.Group differences were also found during feedback processing.Differentiation between blended speech and non‐speech stimuli depends on different processing strategies of the participants ABSTRACT Processing of speech was investigated by using stimuli gradually changing from speech (vowels) to non‐speech (spectral rotated vowels). Stimuli were presented in descending levels of vocalization blends, from pure speech to non‐speech, through step‐wise combinations, resulting in ambiguous versions of the sounds. Participants performed a two‐alternative forced choice task: categorization of sounds were made according to whether they contained more speech or non‐speech. Performance feedback was presented visually on each trial. Reaction times (RT) after sound presentation, and functional magnetic resonance imaging (fMRI) data during auditory and visual processing, were analyzed. RT data suggested individual differences with a distinct group, good performers, functioning better in distinguishing stimuli with a higher degree of ambiguous blends compared to poor performers, who were not able to distinguish these stimuli correctly. fMRI data confirmed this finding. During auditory stimulation, good performers showed neural activation in the ventral auditory pathway, including the primary auditory cortex and the anterior superior temporal sulcus (responsible for speech processing). Poor performers, in contrast, showed neural activation in the dorsal auditory pathway, including the bilateral superior temporal gyrus. Group differences were also found for visual feedback processing. Differences observed between the groups were interpreted as reflecting different neural processing strategies.

Detection of a novelty event in the identification of faces in a passive VEP task

The degree of severity of several psychopathologies coming along with cognitive deficits often impedes the adequate execution of complex cognitive tasks, demanding for objective analysis of cognitive function in an easy-to-follow paradigm for uncooperative patients. The broad availability of electroencephalography (EEG) provides an auspicious base for the development of a fast and reliable tool for the objective diagnosis of pathological cognitive limitations. In the development of the paradigm and follow-up data analysis, we focussed on the objective assessment of the most common cognitive deficits in psychopathological disorders, i.e., limitations in working-memory span and the corresponding loss of attentional resources as well as deficits in facial recognition, contributing to severe social cuts. In a passive face recognition task, we monitored the N170 component of late visual evoked potentials (VEP) in healthy subjects for establishing a methodological base for the diagnostics of cognitive deficits in patients. In line with our preliminary work, we were able to demonstrate a loss of phasic coherence in the single-trial analysis of subsequent visual stimuli during the repetitive face presentation. The novelty event however involuntarily captures attentional resources, resulting in an afresh increase in intertrial phase coherence. These results provide a new viable methodology for accessing the novelty-effect in cognitive deficit patients using a passive visual ERP paradigm of involuntary attentional guidance and habituation.