Learning about trial sequences disrupts the partial reinforcement extinction effect in classical conditioning.

The partial reinforcement extinction effect (PREE) refers to the phenomenon that conditioned responding extinguishes more slowly if subjects had been inconsistently ("partially") reinforced than if they had been reinforced on every trial ("continuously" reinforced). One largely successful account of the PREE, known as sequential theory (Capaldi, 1966), suggests that, when subjects are partially reinforced, they learn that memories of sequences of nonreinforced trials are associated with subsequent reinforcement. This association helps to maintain responding (i.

The sequencing of trials during partial reinforcement affects subsequent extinction.

If a conditioned stimulus or response has been inconsistently ("partially") reinforced, conditioned responding will take longer to extinguish than if responding had been established by consistent ("continuous") reinforcement. This partial reinforcement extinction effect (PREE) is one of the best-known phenomena in associative learning but defies ready explanation by associative models which assume that a partial reinforcement schedule will produce weaker conditioning that should be less resistant to extinction. The most popular explanation of the PREE is that, during partial reinforcement, animals learn that recent nonreinforced (N) trials are associated with subsequent reinforcement (R), and therefore the presence of N trials during extinction serves to promote generalization of conditioning to extinction.

Is cortical inhibition in primary motor cortex related to executive control?

Recent research using paired-pulse transcranial magnetic stimulation (TMS) has shown that the speed with which people can stop an action is linked to GABAergic inhibitory activity in the motor system. Specifically, a significant proportion of the variance in stop signal reaction time (SSRT; a widely used measure of inhibitory control) is accounted for by short-interval cortical inhibition (SICI). It is still unclear whether this relationship reflects a broader link between GABAergic processes and executive functions, or a specific link between GABAergic processes and motor stopping ability.

The effect of staircase stopping accuracy and testing environment on stop-signal reaction time.

The stop-signal task is widely used in experimental psychology and cognitive neuroscience research, as well as neuropsychological and clinical practice for assessing response inhibition. The task requires participants to make speeded responses on a majority of trials, but to inhibit responses when a stop signal appears after the imperative cue. The stop-signal delay after the onset of the imperative cue determines how difficult it is to cancel an initiated action.

The learning curve, revisited.

The nature of the operations that support learning should be evident in the form or shape of the learning curve. For example, models that describe learning as an iterative error-correction process expect that the amount learned on each trial follows a decelerating (negatively inflected) function. That prediction is broadly consistent with the shape of the acquisition and extinction curves derived from mean measures of response strength.

Delaying extinction weakens the partial reinforcement extinction effect.

Conditioned responding that has been extinguished can spontaneously return when the conditioned stimulus (CS) is first presented after an extended delay. This spontaneous recovery of responding suggests that the memory of nonreinforced experience with the CS is impaired over the delay period. Rescorla (2007) provided evidence that this effect of time on nonreinforcement is not specific to extinction.

Does the time-span of conditioning affect spontaneous recovery after extinction?

Gold-standard psychological treatments such as exposure therapy are significantly undermined by high relapse rates. Although exposure-based treatments are capable of extinguishing maladaptive behaviours, these behaviours often spontaneously re-emerge over time - a phenomenon known in experimental research as spontaneous recovery. Understanding the factors that underlie this process is essential to improving long-term treatment outcomes.

In anticipation of pain: expectancy modulates corticospinal excitability, autonomic response, and pain perception.

Pain is a ubiquitous experience encompassing perceptual, autonomic, and motor responses. Expectancy is known to amplify the perceived and autonomic components of pain, but its effects on motor responses are poorly understood. Understanding expectancy modulation of corticospinal excitability has important implications regarding deployment of adaptive and maladaptive protective behaviours in anticipation of pain.

Working memory load reduces corticospinal suppression to former go and trained no-go cues.

Environmental cues associated with an action can prime the motor system, decreasing response times and activating motor regions of the brain. However, when task goals change, the same responses to former go-associated cues are no longer required and motor priming needs to be inhibited to avoid unwanted behavioural errors. The present study tested whether the inhibition of motor system activity to presentations of former go cues is reliant on top-down, goal-directed cognitive control processes using a working memory (WM) load manipulation.

Expected TMS excites the motor system less effectively than unexpected stimulation.

The brain's response to sensory input is modulated by prediction. For example, sounds that are produced by one's own actions, or those that are strongly predicted by environmental cues, elicit an attenuated N1 component in the auditory evoked potential. It has been suggested that this form of sensory attenuation to stimulation produced by one's own actions is the reason we are unable to tickle ourselves.

Linking cortical and behavioural inhibition: Testing the parameter specificity of a transcranial magnetic stimulation protocol.

Across a series of studies, our laboratory has shown that the efficiency of action stopping is associated with the strength of GABA-mediated short-intracortical inhibition (SICI) as measured using transcranial magnetic stimulation (TMS). However, these studies used fixed TMS parameters, which may not optimally probe GABA receptor activity for each individual. In the present study, we measured the relationship between stopping efficiency and SICI using a range of TMS parameters.

Stop Signal Task Training Strengthens GABA-mediated Neurotransmission within the Primary Motor Cortex.

We have recently shown that the efficiency in stopping a response, measured using the stop signal task, is related to GABA-mediated short-interval intracortical inhibition (SICI) in the primary motor cortex. In this study, we conducted two experiments on humans to determine whether training participants in the stop signal task within one session (Experiment 1) and across multiple sessions (Experiment 2) would increase SICI strength. For each experiment, we obtained premeasures and postmeasures of stopping efficiency and resting-state SICI, that is, during relaxed muscle activity (Experiment 1, = 45, 15 male participants) and SICI during the stop signal task (Experiment 2, = 44, 21 male participants).

Pavlovian conditioning under partial reinforcement: The effects of nonreinforced trials versus cumulative conditioned stimulus duration.

A core feature of associative models, such as those proposed by Allan Wagner (Rescorla & Wagner, 1972; Wagner, 1981), is that conditioning proceeds in a trial-by-trial fashion, with increments and decrements in associative strength occurring on each occasion that the conditioned stimulus (conditional stimulus, or CS) is present either with or without the unconditioned stimulus (US). A very different approach has been taken by theories that assume animals continuously accumulate information about the total length of time spent waiting for the US both during the CS and in the absence of the CS (e.g.

Motor cortex dysfunction in problem gamblers.

Impairments in response inhibition have been implicated in gambling psychopathology. This behavioral impairment may suggest that the neural mechanisms involved in response inhibition, such as GABA -mediated neurotransmission in the primary motor cortex (M1), are also impaired. The present study obtained paired-pulse transcranial magnetic stimulation markers of GABA and glutamate receptor activity from the left M1 of three groups-problem gamblers (n = 17, 12 males), at-risk gamblers (n = 29, 19 males), and controls (n = 23, six males)-with each group matched for alcohol use, substance use, and attention-deficit hyperactivity disorder (ADHD) symptomology.

The importance of trials.

Many theories of conditioning describe learning as a process by which stored information about the relationship between a conditioned stimulus (CS) and unconditioned stimulus (US) is progressively updated upon each occasion (trial) that the CS occurs with, or without, the US. These simple trial-based descriptions can provide a powerful and efficient means of extracting information about the correlation between 2 events, but they fail to explain how animals learn about the timing of events. This failure has motivated models of conditioning in which animals learn continuously, either by explicitly representing temporal intervals between events or by sequentially updating an array of associations between temporally distributed elements of the CS and US.

The partial reinforcement extinction effect depends on learning about nonreinforced trials rather than reinforcement rate.

Conditioned responding extinguishes more slowly after partial (inconsistent) reinforcement than after consistent reinforcement. This Partial Reinforcement Extinction Effect (PREE) is usually attributed to learning about nonreinforcement during the partial schedule. An alternative explanation attributes it to any difference in the rate of reinforcement, arguing that animals can detect the change to nonreinforcement more quickly after a denser schedule than a leaner schedule.

Associatively-Mediated Suppression of Corticospinal Excitability: A Transcranial Magnetic Stimulation (TMS) Study.

Response inhibition - the suppression of prepotent behaviours when they are inappropriate - has been thought to rely on executive control. Against this received wisdom, it has been argued that external cues repeatedly associated with response inhibition can come to trigger response inhibition automatically without top-down command. The current project endeavoured to provide evidence for associatively-mediated motor inhibition.

Contralateral and Ipsilateral Relationships between Intracortical Inhibition and Stopping Efficiency.

We have recently shown that the efficiency of stopping a response is correlated with GABAergic activity in primary motor cortex (M1) measured using the short interval intracortical inhibition (SICI) protocol. However, this finding was observed when SICI was measured in left M1 and when stopping efficiency was measured with a bimanual response task. The aim of the present study was to examine the extent to which the relationship between SICI and stopping is lateralized to the hemisphere controlling the response (e.

Hierarchical and Nonlinear Dynamics in Prefrontal Cortex Regulate the Precision of Perceptual Beliefs.

Actions are shaped not only by the content of our percepts but also by our confidence in them. To study the cortical representation of perceptual precision in decision making, we acquired functional imaging data whilst participants performed two vibrotactile forced-choice discrimination tasks: a fast-slow judgment, and a same-different judgment. The first task requires a comparison of the perceived vibrotactile frequencies to decide which one is faster.

Motor Memory: Revealing Conditioned Action Tendencies Using Transcranial Magnetic Stimulation.

can be elicited by motivationally salient stimuli (e.g., appetitive rewards) or objects that support utilization behaviors.

The partial-reinforcement extinction effect does not result from reduced sensitivity to nonreinforcement.

Five experiments used a magazine approach paradigm with rats to investigate whether learning about nonreinforcement is impaired in the presence of a conditioned stimulus (CS) that had been partially reinforced (PRf). Experiment 1 trained rats with a PRf CS and a continuously reinforced (CRf) CS, then extinguished responding to both CSs presented together as a compound. Probe trials of each CS presented alone revealed that extinction was slower for the PRf CS than the CRf CS, despite being extinguished in compound.

Binding identity and orientation in object recognition.

We tested whether an object's orientation is inherently bound to its identity in a holistic view-based representation at the early stages of visual identification, or whether identity and orientation are represented separately. Observers saw brief and masked stimulus sequences containing two rotated objects. They had to detect if a previously cued object was present in the sequence and report its orientation.

Individual differences in intracortical inhibition during behavioural inhibition.

The time required to abort an initiated response can be measured as the Stop Signal Reaction Time (SSRT). We determined whether GABAergic activity in the primary motor cortex (M1), measured using paired-pulse Transcranial Magnetic Stimulation (TMS) was related to SSRT. GABAergic activity in M1 was assessed by measuring Short-Interval Intracortical Inhibition (SICI).

The partial reinforcement extinction effect: The proportion of trials reinforced during conditioning predicts the number of trials to extinction.

Four experiments compared the extinction of responding to a continuously reinforced (CRf) conditioned stimulus (conditional stimulus [CS]) consistently reinforced on every trial, with extinction of responding to a partially reinforced (PRf) CS that had been inconsistently reinforced. To equate the acquisition of responding between the two CSs, the average duration of the CRf CS was extended so that it scheduled the same overall rate of reinforcement per unit time as the PRf CS. Experiment 1 used a within-subjects design to compare the rates of extinction for a 10-s PRf CS reinforced on 33% of trials versus a 30-s CRf CS.

Associations or repetitions? Testing the basis of the Perruchet effect in voluntary response speed.

The Perruchet effect refers to a dissociation between the conscious expectancy of an outcome and the strength or speed of responding in anticipation of that outcome. This dissociation is considered by some to be the best evidence for multiple learning processes with expectancy governed by participants' explicit beliefs and responding driven by the associative history of the cues that partially predict the outcome. However, an alternative nonassociative explanation is that the trends in responding are the result of recent experience with the same outcome (i.