It's all about timing : an electrophysiological examination of feedback-based learning with immediate and delayed feedback

Feedback regarding an individual's action can occur immediately or with a temporal delay. Processing of feedback that varies in its delivery time is proposed to engage different brain mechanisms. fMRI data implicate the striatum in the processing of immediate feedback, and the medial temporal lobe (MTL) in the processing of delayed feedback. The present study offers an electrophysiological examination of feedback processing in the context of timing, by studying the effects of feedback timing on the feedback-related negativity (FRN), a product of the midbrain dopamine system, and elucidating whether the N170 ERP component could capture MTL activation associated with the processing of delayed feedback. Participants completed a word-object paired association learning task; they received feedback 500 ms (immediate feedback condition) following a button press during the learning of two sets of 14 items, and at a delay of 6500 ms (delayed feedback condition) during the learning of the other two sets. The results indicated that while learning outcomes did not differ under the two timing conditions, Event Related Potential (ERPs) pointed to differential activation of the examined ERP components. FRN amplitude was found to be larger following the immediate feedback condition when compared with the delayed feedback condition, and sensitive to valence and learning only under the immediate feedback condition. Additionally, the amplitude of the N170 was found larger following the delayed feedback condition when compared with the immediate feedback condition. Taken together, the findings of the present study support the contention that the processing of delayed feedback involves a shift away from midbrain dopamine activation to the recruitment of the MTL

Suppressing visual feedback in written composition: Effects on processing demands and coordination of the writing processes

The goal of this experiment was to investigate the role of visual feedback during written composition. Effects of suppression of visual feedback were analysed both on processing demands and on on-line coordination of low-level execution processes and of high-level conceptual and linguistic processes. Writers composed a text and copied it either with or without visual feedback. Processing demands of the writing processes were evaluated with reaction times to secondary auditory probes that were analysed according to whether participants were handwriting (in a composing and a copying tasks) or engaged in high level processes (when pausing in a composing task). Suppression of visual feedback increased reaction times interference (secondary reaction time minus baseline reaction time) during handwriting in the copying task and not during pauses in the composing task. This suggests that suppression of visual feedback affected processing demands of only execution processes and not those of high-level conceptual and linguistic processes. This is confirmed by analysis of quality of the texts produced by participants that were little, if any, affected by the suppression of visual feedback. Results also indicate that the increase in processing demands of execution related to suppression of visual feedback affected on-line coordination of the writing processes. Indeed, when visual feedback was suppressed, reaction time interferences associated to handwriting were not reliable different in the copying task and in the composing task but were significantly different in the composition task, RT interference associated to handwriting being lower in the copying task than in the composition task. When visual feedback was suppressed, writers activated step-by-step execution processes and high-level writing processes, whereas they concurrently activated these writing processes when composing with visual feedback

Feedback loop compensates for rectifier nonlinearity

Signal processing circuit with two negative feedback loops rectifies two sinusoidal signals which are 180 degrees out of phase and produces a single full-wave rectified output signal. Each feedback loop incorporates a feedback rectifier to compensate for the nonlinearity of the circuit

The effect of continuous, nonlinearly transformed visual feedback on rapid aiming movements

We investigated the ability to adjust to nonlinear transformations that allow people to control external systems like machines and tools. Earlier research (Verwey and Heuer 2007) showed that in the presence of just terminal feedback participants develop an internal model of such transformations that operates at a relatively early processing level (before or at amplitude specification). In this study, we investigated the level of operation of the internal model after practicing with continuous visual feedback. Participants executed rapid aiming movements, for which a nonlinear relationship existed between the target amplitude seen on the computer screen and the required movement amplitude of the hand on a digitizing tablet. Participants adjusted to the external transformation by developing an internal model. Despite continuous feedback, explicit awareness of the transformation did not develop and the internal model still operated at the same early processing level as with terminal feedback. Thus with rapid aiming movements, the type of feedback may not matter for the locus of operation of the internal model

Training of Working Memory Impacts Neural Processing of Vocal Pitch Regulation

Working memory training can improve the performance of tasks that were not trained. Whether auditory-motor integration for voice control can benefit from working memory training, however, remains unclear. The present event-related potential (ERP) study examined the impact of working memory training on the auditory-motor processing of vocal pitch. Trained participants underwent adaptive working memory training using a digit span backwards paradigm, while control participants did not receive any training. Before and after training, both trained and control participants were exposed to frequency-altered auditory feedback while producing vocalizations. After training, trained participants exhibited significantly decreased N1 amplitudes and increased P2 amplitudes in response to pitch errors in voice auditory feedback. In addition, there was a significant positive correlation between the degree of improvement in working memory capacity and the post-pre difference in P2 amplitudes. Training-related changes in the vocal compensation, however, were not observed. There was no systematic change in either vocal or cortical responses for control participants. These findings provide evidence that working memory training impacts the cortical processing of feedback errors in vocal pitch regulation. This enhanced cortical processing may be the result of increased neural efficiency in the detection of pitch errors between the intended and actual feedback

On the neural computation of utility

The rewarding effect produced by electrical stimulation of the lateral hypothalamus can compete and summate with gustatory rewards. However, physiological manipulations, such as sodium depletion and the accumulation of an energy-rich solution in the gut, can alter the rewarding impact of the gustatory stimuli without producing substantial changes in the rewarding effect of the electrical stimulation. On the basis of their competition and summation, it is argued that the artificial and natural rewards are evaluated in a common currency, represented in an aggregate firing-rate code. Such a code would make it possible for the synchronous, spatially contiguous pattern of neural firing induced by the electrode to simulate a signal normally produced by asynchronous, spatially distributed activity. It is suggested that a unidimensional code of this sort is employed to represent the utility of a goal object. In order for physiological feedback to alter the utility of one natural reward, such as sucrose, without changing the utility of a second natural reward, such as a salt solution, the physiological feedback signals must enter into the computation of utility at a stage of processing in which the representations of the two natural rewards are distinct. However, orderly choice between such rewards implies that their utilities are expressed ultimately in a common neural currency. That physiological feedback alters the rewarding effects of the gustatory stimuli suggests that the physiological feedback signals modulate the value of such natural stimuli at a stage of processing prior to their translation into a common currency. In contrast, physiological feedback would fail to alter the rewarding effect of the electrical stimulation if the electrically evoked signal is injected at a later stage processing, a stage in which different rewards are represented in a common currency. In this view, the signal injected by the electrical stimulation mimics the utility of a natural stimulus but not its sensory quality

Does Corticothalamic Feedback Control Cortical Velocity Tuning?

The thalamus is the major gate to the cortex and its contribution to cortical receptive field properties is well established. Cortical feedback to the thalamus is, in turn, the anatomically dominant input to relay cells, yet its influence on thalamic processing has been difficult to interpret. For an understanding of complex sensory processing, detailed concepts of the corticothalamic interplay need yet to be established. To study corticogeniculate processing in a model, we draw on various physiological and anatomical data concerning the intrinsic dynamics of geniculate relay neurons, the cortical influence on relay modes, lagged and nonlagged neurons, and the structure of visual cortical receptive fields. In extensive computer simulations we elaborate the novel hypothesis that the visual cortex controls via feedback the temporal response properties of geniculate relay cells in a way that alters the tuning of cortical cells for speed.Comment: 31 pages, 7 figure

Sentence processing with incremental feedback

Utilizing recurrent network topologies to produce case/role meaning representations for single sentences has become common practice in connectionist natural language processing systems. Typically, these systems train with the complete sentence meaning as the target output for the entire period that the sentence is being processed; i.e., the complete meaning is available starting with the first word of the sentence. Thus, the context feedback provided by these systems is non-incremental in that they use information about the sentence that has not yet been encountered in order to aid in the processing and learning tasks. SAIL1 is a connectionist natural language processing system which builds the sentence meaning representation incrementally, incorporating into the meaning only the information derived from words already processed