Efficient Inhibitory Control Research Articles

Individual differences in intracortical inhibition predict action control when facing emotional stimuli.

Efficient inhibitory control in the context of prepotent actions is vital. However, such action inhibition may be profoundly influenced by affective states. Interestingly, research indicates that action control can be either impaired or improved by emotional stimuli. Thus, a great deal of confusion surrounds our knowledge of the complex dynamics subtending emotions and action control. Here, we aimed to investigate whether negative stimuli, even when non-consciously presented and task-irrelevant, can affect action control relative to neutral stimuli. Additionally, we tested whether individual differences in intracortical excitability may predict action control capabilities. To address these issues, we asked participants to complete a modified version of the Stop Signal Task (SST) in which fearful or neutral stimuli were subliminally presented before the go signals as primes. Moreover, we assessed participants' resting-state corticospinal excitability, short intracortical inhibition (SICI), and intracortical facilitation (ICF). Results demonstrated better action control capabilities when fearful stimuli were subliminally presented and interindividual SICI predicted stronger action inhibition capabilities. Taken together, these results shed new light on the intricate dynamics between action, consciousness, and motor control, suggesting that intracortical measures can be used as potential biomarkers of reduced motor inhibition in research and clinical settings.

Individual differences in executive attention and inhibitory control are related to spatial memory biases in adults.

Executive attention is involved in working memory; however, the role of executive attention in the maintenance of information in spatial working memory is debated. This study examined whether inhibitory control was related to spatial working memory biases in adults in a simple spatial memory task where participants had to remember one location on an otherwise blank computer screen. On some trials, a distractor was presented during the maintenance period. Eighty-four participants completed the spatial working memory task and a battery of cognitive control measures. When a distractor was presented during the maintenance period of the spatial memory task, performance on two of the cognitive control measures, a measure of overall attention and a measure of inhibitory control was related to memory errors. When a distractor was not presented during the spatial memory task, memory errors were not related to performance on the cognitive control tasks. Overall, these effects demonstrated that attention is related to maintaining locations in spatial working memory in adults, and inhibitory control may also be related such that those with more efficient inhibitory control were less influenced by distractors presented during the maintenance period.

Frozen in (e)motion: How reactive motor inhibition is influenced by the emotional content of stimuli in healthy and psychiatric populations

Efficient inhibitory control is vital. However, environmental cues can influence motor control especially in an emotional context. One common task to measure inhibitory control is the stop-signal task (SST), which asks participants to respond to go stimuli knowing that on some trials a stop signal will be presented, requiring them to inhibit their response. This paradigm estimates the ability to inhibit already-initiated responses by calculating participants' stop-signal reaction times (SSRT), an index of inhibitory control. Here, we aim to review the existing, often contradictory, evidence on the influence of emotional stimuli on the inhibitory process. We aim to discuss which factors may reveal an interference as well as an advantage of emotional stimuli on action inhibition performance. Finally, we review the existing evidence that has investigated the effect of such stimuli on action inhibition in the psychiatric population. Important factors are the relevance, the intensity and the valence of the emotional stimulus, as well as the affected component of the motor control. From all this evidence, it is clear that understand precisely how emotion is integrated into core executive functions, such as inhibitory control, is essential not only for cognitive neuroscience, but also for refining neurocognitive models of psychopathology.

Emotional devaluation in ignoring and forgetting as a function of adolescent development

We know that emotion and cognition interact to guide goal-directed behavior. Accordingly, it has recently been shown that distracting stimuli (Raymond, Fenske, & Tavassoli, 2003) and instructed to-be-forgotten items (Vivas, Marful, Panagiotidou, & Bajo, 2016) are emotionally devaluated. The devaluation by inhibition hypothesis (Raymond, Fenske, & Tavassoli, 2003) is the main theoretical explanation of these effects. However, we know little about how the cognition-emotion interplay is further modulated by development, and particularly, by changes in inhibitory control and affective processing within the adolescence period. In the present study we combined a selective attention task with faces, and a selective memory (directed forgetting paradigm) task with words, with a pleasantness evaluation task to address this question in three age groups; younger adolescents, older adolescents and young adults. Younger adolescents exhibited worse accuracy in the attention task, lower overall recognition of words in the memory task, and a smaller in magnitude directed forgetting effect in the latter, relative to the two older groups. That is, they showed less efficient inhibitory control in attention and memory selection. Despite this, all groups showed similar devaluation effects of the distractor faces and the to-be-forgotten words. Our findings do not fully support an inhibition account of such effects. Yet, they support the robustness of the forgetting devaluation effect, replicating the findings of Vivas, Marful, Panagiotidou, and Bajo (2016) with a Greek version of the task and in a bigger sample of participants.

The effect of experience and olfactory cue in an inhibitory control task in guppies, Poecilia reticulata

Behavioural responses to the environment often require the suppression of strong internal predispositions or the overriding of external lures, tasks performed by a cognitive function called inhibitory control. Inhibitory control of nonhuman animals is generally measured with the cylinder task: subjects are presented with food inside a transparent cylinder and must inhibit their tendency to reach the food directly and instead detour round the cylinder to solve the task. However, several studies have raised concerns about the validity of this test to compare different species. Recently, a tiny teleost fish, the guppy, Poecilia reticulata, was tested with the cylinder task and scored higher than many mammals and birds. Before considering that guppies display unpredictably high inhibitory control, it is important to exclude that they were advantaged by some noncognitive factors. In particular, guppies could enjoy three advantages: experience with transparent surfaces (i.e. the walls of maintenance aquaria), experience with detouring round see-through obstacles (vegetation in the maintenance aquaria) and the spread of food odour in the water from the sides of the cylinder. We tested whether these factors affect guppies' performance in the cylinder task by manipulating both their experience with transparent surfaces before the task and the diffusion of food odour cues from the cylinder. Guppies raised in transparent aquaria or with transparent panels placed inside the tank did not show advantages over guppies with no experience with transparent surfaces. Furthermore, the guppies’ performance was not reduced when the cylinder was pierced in the middle, so that both visual and olfactory cues lured them in the same direction. These results seem to exclude methodological explanations for the high inhibitory control score of guppies, and they indicate that even teleost fish can display efficient inhibitory control.

Motor inhibition efficiency in healthy aging: the role of γ-aminobutyric acid.

The ability to cancel a motor response is critical for optimal functioning in various facets of daily life. Hence, efficient inhibitory motor control is a key function throughout the lifespan. Considering the fact that inhibitory motor function gradually declines with advancing age, it is not surprising that the study of motor inhibition in this age group is gaining considerable interest. In general, we can distinguish between two prominent types of motor inhibition, namely proactive and reactive inhibition. Whereas the anticipation for upcoming stops (proactive inhibition) appears readily preserved at older age, the ability to stop an already planned or initiated action (reactive inhibition) generally declines with advancing age. The differential impact of aging on proactive and reactive inhibition at the behavioral level prompts questions about the neural architecture underlying both types of inhibitory motor control. Here we will not only highlight the underlying structural brain properties of proactive and reactive inhibitory control but we will also discuss recent developments in brain-behavioral approaches, namely the registration of neurochemical compounds using magnetic resonance spectroscopy. This technique allows for the direct detection of the primary inhibitory neurotransmitter in the brain, i.e., γ-aminobutyric acid, across the broader cortical/subcortical territory, thereby opening new perspectives for better understanding the neural mechanisms mediating efficient inhibitory control in the context of healthy aging. Ultimately, these insights may contribute to the development of interventions specifically designed to counteract age-related declines in motor inhibition.

Fish perform like mammals and birds in inhibitory motor control tasks

Inhibitory control is an executive function that positively predicts performance in several cognitive tasks and has been considered typical of vertebrates with large and complex nervous systems such as primates. However, evidence is growing that some fish species have evolved complex cognitive abilities in spite of their relatively small brain size. We tested whether fish might also show enhanced inhibitory control by subjecting guppies, Poecilia reticulata, to the motor task used to test warm-blooded vertebrates. Guppies were trained to enter a horizontal opaque cylinder to reach a food reward; then, the cylinder was replaced by a transparent one, and subjects needed to inhibit the response to pass thought the transparency to reach the food. Guppies performed correctly in 58% trials, a performance fully comparable to that observed in most birds and mammals. In experiment 2, we tested guppies in a task with a different type of reward, a group of conspecifics. Guppies rapidly learned to detour a transparent barrier to reach the social reward with a performance close to that of experiment 1. Our study suggests that efficient inhibitory control is shown also by fish, and that its variation between-species is only partially explained by variation in brain size.

NEURAL CORRELATES OF REACTION TIME VARIABILITY IN OLDER ADULTS PERFORMING A MULTI-SOURCE INTERFERENCE TASK

A growing body of literature describes older adults showing decline in cognitive control (top-down executive control) that is associated with frontal lobe change. Traditional neuropsychological tests examining frontal dysfunction, such as the Stroop and the Trail Making tests, measure individual's top-down control ability by comparing the time taken to complete the task in control condition and the interference condition. Trial-by-trial intra-individual reaction time (RT) variability in cognitive control tasks, however, could also be a sensitive measure of frontal integrity, since it has been shown that frontal involvement is critical in maintaining cognitive stability by minimizing fluctuation of cognitive performance. In this study, we purported to investigate the neural correlates of intra-individual RT variability in an experimental cognitive control task, namely the Multi-Source Interference Task (MSIT). Utilizing functional magnetic resonance imaging (fMRI), we investigated the brain regions activated when healthy older adults (n=52) performed the MSIT, which consists of interference and control conditions. Regional activation that was significantly different in the interference condition compared to the control condition was examined to find brain regions involved in inhibitory control. Within the regions found to be involved in inhibitory control, we identified regions that were specifically associated with the intra-individual RT variability. Inhibitory success was correlated with smaller intra-individual variability of RT, while the magnitude of the variability was reflected in the activation of the frontal regions, such as the left middle and left inferior frontal gyri, as well as the left supramarginal gyrus. Individuals with greater intra-individual variability during the MSIT activated the inhibitory control network to a greater magnitude, possibly reflecting the increased demand for cognitive control network due to their less efficient inhibitory control system. This is consistent with previous findings that showed greater intra-individual variability in dementia patients with frontal involvement compared to those with Alzheimer's disease. Increase in intra-individual variability of RT has also been shown to be observed in people with MCI, suggesting the measure as a promising behavioral index that reflects frontal or frontoparietal integrity.

High body mass index is associated with impaired cognitive control

The prevalence of weight problems is increasing worldwide. There is growing evidence that high body mass index (BMI) is associated with frontal lobe dysfunction and cognitive deficits concerning mental flexibility and inhibitory control efficiency.The present study aims at replicating and extending these observations. We compared cognitive control performance of normal weight (BMI < 25) and overweight (BMI ≥ 25) university students on a task tapping either inhibitory control (Experiment 1) or interference control (Experiment 2). Experiment 1 replicated previous findings that found less efficient inhibitory control in overweight individuals. Experiment 2 complemented these findings by showing that cognitive control impairments associated with high BMI also extend to the ability to resolve stimulus-induced response conflict and to engage in conflict-driven control adaptation. The present results are consistent with and extend previous literature showing that high BMI in young, otherwise healthy individuals is associated with less efficient cognitive control functioning.

Inhibitory control and response monitoring are not systematically related to weekly alcohol consumption in the general population.

In alcohol use disorder, deficits in cognitive control (i.e., inhibition and response monitoring) might underlie the loss of self-control and, thereby, failure to adjust alcohol consumption in response to associated negative consequences. According to the continuum hypothesis, the magnitude of these deficits should be related in a stair-case manner, with the greatest deficits among its heaviest consumers. The current study aims at investigating this association in the general population. This is a cross-sectional study of 397 participants aged 18-64years, who self-reported their mean weekly alcohol consumption and were assessed with the stop-signal task, estimating inhibitory efficiency (stop-signal reaction time; SSRT) and response monitoring (post-error slowing; PES). Set-shifting ability was investigated by the intra-extra dimensional (IED) set-shifting task. Three ANCOVAs were performed with SSRT, PES, and IED as the dependent variables (DV), respectively, and alcohol consumption levels as the independent variable. Covariates were included when they were significantly associated with the DV. Compared to the teetotalers, all levels of alcohol consumption were significantly associated to lower SSRT, which implies more efficient inhibitory control; however, there was no significant difference in SSRT between other consumption levels. The two highest consumption groups had significantly shorter PES when compared to teetotalers and/or the lowest consumption group, implying less behavioral adjustment after failures. IED was not significantly related to the alcohol consumption levels. There was no stair-case relation between weekly consumption levels and cognitive control functions within this general population, which might be due to the limited consumption range investigated.

Delayed N2 response in Go condition in a visual Go/Nogo ERP study in children who stutter

Purpose of the studyThe main aim of the study was to investigate the attentional and inhibitory abilities and their underlying processes of children who stutter by using behavioural measurement and event-related potentials (ERP) in a visual Go/Nogo paradigm. MethodsParticipants were 11 children who stutter (CWS; mean age 8.1, age range 6.3–9.5 years) and 19 typically developed children (TDC; mean age 8.1, age range 5.8–9.6 years). They performed a visual Go/Nogo task with simultaneous EEG recording to obtain ERP responses. ResultsResults showed that CWS had longer N2 and P3 latencies in the Go condition compared to the TDC. In contrast, the groups did not differ significantly in the Nogo condition or behavioural measures. ConclusionsOur findings did not confirm less efficient inhibitory control in CWS but suggest atypical attentional processing such as stimulus evaluation and response selection.Educational Objectives: The reader will be able to (a) describe recent findings on attention and inhibitory control in children who stutter, (b) describe the measurement of attentional processing, including inhibitory control, and (c) describe the findings on attentional processing in children who stutter as indexed by the event-related potentials in a visual Go/Nogo paradigm.

Control of Auditory Attention in Children With Specific Language Impairment.

Children with specific language impairment (SLI) appear to demonstrate deficits in attention and its control. Selective attention involves the cognitive control of attention directed toward a relevant stimulus and simultaneous inhibition of attention toward irrelevant stimuli. The current study examined attention control during a cross-modal word recognition task. Twenty participants with SLI (ages 9-12 years) and 20 age-matched peers with typical language development (TLD) listened to words through headphones and were instructed to attend to the words in 1 ear while ignoring the words in the other ear. They were simultaneously presented with pictures and asked to make a lexical decision about whether the pictures and auditory words were the same or different. Accuracy and reaction time were measured in 5 conditions, in which the stimulus in the unattended channel was manipulated. The groups performed with similar accuracy. Compared with their peers with TLD, children with SLI had slower reaction times overall and different within-group patterns of performance by condition. Children with TLD showed efficient inhibitory control in conditions that required active suppression of competing stimuli. Participants with SLI had difficulty exerting control over their auditory attention in all conditions, with particular difficulty inhibiting distractors of all types.

The inhibitory cotrol function in patients with anorexia nervosa

Objective To investigate the differences in inhibitory control function between patients with anorexia nervosa (AN) and healthy controls. Methods A case-control study was utilized in this research. 47 patients with AN and 43 matched healthy-control (HC) were included in this study. Information about function of inhibitory control was gathered by means of self-reported inventory including Barratt Impulsiveness Scale (BIS) and a behavioral measure named Stop Signal Task. Results 1.Self-reported inventory of BIS: there was no significant difference between AN and HC in BIS total score ((66.40±8.72) vs (65.49±8.72)) and subscale(Attentional imp.(13.15±2.52) vs (13.14±2.60), Motor imp.(18.34±2.71) vs (19.02±3.32), Non-planning imp.(24.26±4.44) vs (23.14±3.97))(P>0.05). 2.In behavioral measures, AN group showed significantly decreased in SSRT score((340.66±54.70)ms vs (363.55±39.08)ms, P=0.033), indicating that patients with AN had more efficient inhibitory control. Conclusion AN is characterized by hyperfunction of inhibitory control. Key words: Anorexia nervosa; Inhibitory control; Stop signal task

The role of trait impulsivity in response inhibition: Event-related potentials in a stop-signal task

The study examined the relation between self-reported impulsivity and inhibitory control in normal individuals. We compared stopping performance and neural correlates of stopping on stop-signal task between participants who scored in the top (n=12) and bottom 25% (n=12) on Impulsivity Scale from a sample of 305 male adults. Participants scoring high on impulsivity did not show impaired inhibitory control. However, it seems that the high impulsive tended to make more errors of commission and omission. Enhanced N1 amplitudes were found in successful than failed inhibition trials. The high impulsive group had smaller P3 amplitude than the low impulsive group. It appears that the high impulsive group may have a less efficient inhibitory control. Impulsivity Scale non-planning impulsiveness score and inattention score of Adult ADHD Self-Report Scale (ASRS) were negatively correlated with P3 amplitudes on successful inhibition trails, suggesting that impulsivity could have the potential influence on inhibitory control.

Integrating impairments in reaction time and executive function using a diffusion model framework.

Using Ratcliff's diffusion model and ex-Gaussian decomposition, we directly evaluate the role individual differences in reaction time (RT) distribution components play in the prediction of inhibitory control and working memory (WM) capacity in children with and without ADHD. Children with (n = 91, [Formula: see text] age = 10.2years, 67% male) and without ADHD (n = 62, [Formula: see text] age = 10.6years, 46% male) completed four tasks of WM and a stop signal reaction time (SSRT) task. Children with ADHD had smaller WM capacities and less efficient inhibitory control. Diffusion model analyses revealed that children with ADHD had slower drift rates (v) and faster non-decision times (Ter), but there were no group differences in boundary separations (a). Similarly, using an ex-Gaussian approach, children with ADHD had larger τ values than non-ADHD controls, but did not differ in μ or σ distribution components. Drift rate mediated the association between ADHD status and performance on both inhibitory control and WM capacity. τ also mediated the ADHD-executive function impairment associations; however, models were a poorer fit to the data. Impaired performance on RT and executive functioning tasks has long been associated with childhood ADHD. Both are believed to be important cognitive mechanisms to the disorder. We demonstrate here that drift rate, or the speed at which information accumulates towards a decision, is able to explain both.

Plastic modifications within inhibitory control networks induced by practicing a stop-signal task: An electrical neuroimaging study

IntroductionInhibitory control refers to our ability to suppress ongoing motor, affective or cognitive processes and mostly depends on a fronto–basal brain network. Inhibitory control deficits participate in the emergence of several prominent psychiatric conditions, including attention deficit/hyperactivity disorder or addiction. The rehabilitation of these pathologies might therefore benefit from training-based behavioral interventions aiming at improving inhibitory control proficiency and normalizing the underlying neurophysiological mechanisms. The development of an efficient inhibitory control training regimen first requires determining the effects of practicing inhibition tasks. MethodsWe addressed this question by contrasting behavioral performance and electrical neuroimaging analyses of event-related potentials (ERPs) recorded from humans at the beginning versus the end of 1 h of practice on a stop-signal task (SST) involving the withholding of responses when a stop signal was presented during a speeded auditory discrimination task. ResultsPracticing a short SST improved behavioral performance. Electrophysiologically, ERPs differed topographically at 200 msec post-stimulus onset, indicative of the engagement of distinct brain network with learning. Source estimations localized this effect within the inferior frontal gyrus, the pre-supplementary motor area and the basal ganglia. ConclusionOur collective results indicate that behavioral and brain responses during an inhibitory control task are subject to fast plastic changes and provide evidence that high-order fronto–basal executive networks can be modified by practicing a SST.

Salience network integrity predicts default mode network function after traumatic brain injury

Efficient behavior involves the coordinated activity of large-scale brain networks, but the way in which these networks interact is uncertain. One theory is that the salience network (SN)--which includes the anterior cingulate cortex, presupplementary motor area, and anterior insulae--regulates dynamic changes in other networks. If this is the case, then damage to the structural connectivity of the SN should disrupt the regulation of associated networks. To investigate this hypothesis, we studied a group of 57 patients with cognitive impairments following traumatic brain injury (TBI) and 25 control subjects using the stop-signal task. The pattern of brain activity associated with stop-signal task performance was studied by using functional MRI, and the structural integrity of network connections was quantified by using diffusion tensor imaging. Efficient inhibitory control was associated with rapid deactivation within parts of the default mode network (DMN), including the precuneus and posterior cingulate cortex. TBI patients showed a failure of DMN deactivation, which was associated with an impairment of inhibitory control. TBI frequently results in traumatic axonal injury, which can disconnect brain networks by damaging white matter tracts. The abnormality of DMN function was specifically predicted by the amount of white matter damage in the SN tract connecting the right anterior insulae to the presupplementary motor area and dorsal anterior cingulate cortex. The results provide evidence that structural integrity of the SN is necessary for the efficient regulation of activity in the DMN, and that a failure of this regulation leads to inefficient cognitive control.

Estrogen modulates inhibitory control in healthy human females: evidence from the stop-signal paradigm

Animal studies point to a role of estrogen in explaining gender differences in striatal dopaminergic functioning, but evidence from human studies is still lacking. Given that dopamine is crucial for controlling and organizing goal-directed behavior, estrogen may have a specific impact on cognitive control functions, such as the inhibition of prepotent responses. We compared the efficiency of inhibitory control (as measured by the stop-signal task) in young women across the three phases of their menstrual cycle (salivary estradiol and progesterone concentrations were assessed) and in young men. Women were less efficient in inhibiting prepotent responses in their follicular phase, which is associated with higher estradiol levels and with higher dopamine turnover rates, than in their luteal or menstruation phase. Likewise, women showed less efficient inhibitory control than men in their follicular phase but not in their luteal or menstruation phase. Our results are consistent with models assuming that the over-supply of striatal dopamine in the follicular phase weakens inhibitory pathways, thus leading to enhanced competition between responses. We conclude that gender differences in response inhibition are variable and state dependent but not structural.

The Role of Interference Control in Working Memory: A Study with Children at Risk of Adhd

The study aimed to test whether the impairment in a working memory task observed in children at risk of ADHD was due to a lack of control of interfering information being processed whilst carrying out the memory task. Two groups of children at risk of ADHD with or without a learning disability (reading impairment) were compared to a control group in a working memory task. Activation of irrelevant items was tested with a lexical decision task presented immediately after the final recall in about half of the trials. Results showed a poor working memory performance in children at risk of ADHD and reading disability associated with a larger activation of irrelevant information than that of control children. Results indicated that the to-be-excluded and interfering items are still highly accessible to working memory in children that fail the working memory task. The examination of working memory and interference control of children at risk of ADHD with a learning disability revealed a counterintuitive picture of children with poor working memory showing better recall/activation of processed information. This picture is consistent with a view of working memory related to an efficient inhibitory control that influences cognitive functioning.

Propagation Dynamics of Epileptiform Activity Acutely Induced by Bicuculline in the Hippocampal–Parahippocampal Region of the Isolated Guinea Pig Brain

Aim of the study is to investigate the involvement of parahippocampal subregions in the generation and in the propagation of focal epileptiform discharges in an acute model of seizure generation in the temporal lobe induced by arterial application of bicuculline in the in vitro isolated guinea pig brain preparation. Electrophysiological recordings were simultaneously performed with single electrodes and multichannel silicon probes in the entorhinal, perirhinal, and piriform cortices and in the area CA1 of the hippocampus of the in vitro isolated guinea pig brain. Interictal and ictal epileptiform discharges restricted to the temporal region were induced by a brief (3-5 min) arterial perfusion of the GABA(A) receptor antagonist, bicuculline methiodide (50 microM). Current source density analysis of laminar field profiles performed with the silicon probes was carried out at different sites to establish network interactions responsible for the generation of epileptiform potentials. Nonlinear regression analysis was conducted on extracellular recordings during ictal onset in order to quantify the degree of interaction between fast activities generated at different sites, as well as time delays. Experiments were performed in 31 isolated guinea pig brains. Bicuculline-induced interictal and ictal epileptiform activities that showed variability of spatial propagation and time course in the olfactory-temporal region. The most commonly observed pattern (n = 23) was characterized by the initial appearance of interictal spikes (ISs) in the piriform cortex (PC), which propagated to the lateral entorhinal region. Independent and asynchronous preictal spikes originated in the entorhinal cortex (EC)/hippocampus and progressed into ictal fast discharges (around 25 Hz) restricted to the entorhinal/hippocampal region. The local generation of fast activity was verified and confirmed both by CSD and phase shift analysis performed on laminar profiles. Fast activity was followed by synchronous afterdischarges that propagated to the perirhinal cortex (PRC) (but not to the PC). Within 1-9 min, the ictal discharge ceased and a postictal period of depression occurred, after which periodic ISs in the PC resumed. Unlike preictal ISs, postictal ISs propagated to the PRC. Several studies proposed that reciprocal connections between the entorhinal and the PRC are under a very efficient inhibitory control (1). We report that ISs determined by acute bicuculline treatment in the isolated guinea pig brain progress from the PC to the hippocampus/EC just before ictal onset. Ictal discharges are characterized by a peculiar pattern of fast activity that originates from the entorhinal/hippocampal region and only secondarily propagates to the PRC. Postictal propagation of ISs to the PRC occurred exclusively when an ictal discharge was generated in the hippocampal/entorhinal region. The results suggest that reiteration of ictal events may promote changes in propagation pattern of epileptiform discharges that could act as trigger elements in the development of temporal lobe epilepsy.