Stopping action and cognition

Chair:   René J. Huster

Experimental Psychology Lab, Institute for Psychology, University of Oldenburg

Abstract:

The ability to stop responses or thoughts is one of a family of functions commonly
referred to as cognitive control. The interplay of these processes enables the
adaptation to an ever-changing environment. Maladaptive behavior is a logical and
common consequence of impairments in cognitive control. Indeed, especially
attenuated capabilities to control or inhibit inappropriate cognitions and responses
have been shown to be associated with a variety of psychiatric conditions.
In this symposium we will highlight eminent topics with respect to response inhibition.
Recently, a differentiation of proactive and reactive inhibition mechanisms was
brought forward. We will discuss the role of top-down control in reactive and
proactive stopping based on differential engagement of a fronto-basal ganglia
network caused by variations in anticipated need for response inhibition. The
involvement of neocortical regions in these mechanisms is further elucidated by
considering behavioral and electrophysiological consequences of prefrontal lesions.
Of note, especially measures derived from recordings of the electroencephalogram
(EEG) during processing of stop signal or go/nogo tasks are often interpreted as
indicators of inhibitory capabilities. As will be shown, however, the most commonly
studied event-related potentials - the N200 and P300 - do not serve as indices of a
proper inhibition process. At last, data from a meta-analysis will be presented that
indicate that the reported global deficits in executive functioning associated with
schizophrenia are due to a reduced ability of cognitive inhibition.

Talk 1:

Electroencephalographic indicators of response inhibition: Where to look?

René J. Huster, Stefanie Enriquez-Geppert, Christoph S. Herrmann
Experimental Psychology Lab, Institute for Psychology, University of Oldenburg, Germany

Response inhibition paradigms, whose most famous representatives are stop signal
and go/nogo tasks, are often used to study cognitive control processes. Because of
the apparent demand to suppress motor reactions, the electrophysiological
responses evoked by stop and nogo trials have sometimes likewise been interpreted
as indicators of inhibitory processes. Recent research as well as current theories on
the families of N200- and P300-like potentials, however, suggest a richer conceptual
background.
We shortly review studies stressing a functional differentiation of the N200 and P300,
a finding further supported by differences in generator constellations giving rise to
these event-related potentials. Results from experiments manipulating stimulus
probabilities and response priming will be presented showing that neither the N200
nor the P300 serve as unambiguous indicators of a proper inhibitory process. The
N200 rather seems to reflect the monitoring of conflicts in information processing.
Although the exact functional correspondence of the P300 is still elusive, recent
findings at least support an association with evaluative processing of response
alternatives.
However, recently it was suggested that when subjected to time-frequency
compositions, EEG responses reveal differences between go and stop trials in the
beta frequency range which might more directly reflect inhibitory processing. Data
from single-trial EEG of a stop signal task indeed support differential associations of
delta, theta and beta frequency components with inhibition success.

Talk 2:

Meta-analytic evidence for impaired cognitive inhibition in schizophrenia.

René Westerhausen, Kristiina Kompus, Kenneth Hugdahl
Department of Biological and Medical Psychology, University of Bergen, Norway;
Division of Psychiatry, Haukeland University Hospital, N-5009 Bergen, Norway

Meta-analyses unambiguously indicate an impairment of executive functioning in
schizophrenia. However, these previous studies treat executive functions as unitary
cognitive faculty, pooling the results of different paradigms and neuropsychological
instruments, and ignoring that executive functions can also be seen as group of
partially independent cognitive sub-components, such as updating, shifting, or
inhibition. The present meta-analysis focused on the schizophrenia-related
impairment in the sub-component of cognitive inhibition as represented by the color-
word interference effect in the Stroop paradigm. The analysis was based on 36
studies which in total included 1081 patients and 1026 healthy controls. A fixed-effect
analyses – using the effect size statistic Hedges’ g for the differences between
patients and healthy controls in the interference effect as dependent variables –
revealed that patients exhibit an increased interference effect (M(g) = 0.43; CI95%:
0.35-0.52; Z = 9.62, p<0.0001; Fail Safe N = 828). A significant meta-regression
analysis (b = -0.44; t(32) = -2.88, p=0.007) further showed that the card version (M(g)
= 0.60) of the Stroop paradigm produces a larger effect size than the single-trial
computerized version (M(g) = 0.19). The overall group difference indicates that the
reported global deficits in executive functioning in schizophrenia are at least partly
due to reduced cognitive inhibition. However, the differences in mean effect size
between card and computerized version also indicate that methodological aspects
(even within the same paradigm) significantly affect the results and need to be
considered when assessing clinical groups.

Talk 3:

The role of top-down control in reactive and proactive stopping

Sara Jahfari^1,2, Fredrick Verbruggen³, Michael J. Frank⁴, Lourens Waldorp¹, Lorenza Colzato⁵, K. Richard Ridderinkhof^1,2 & Birte U. Forstmann^1,2
1 Department of Psychology, University of Amsterdam, The Netherlands
² Cognitive Science Center Amsterdam, University of Amsterdam, The Netherlands
³ School of Psychology, University of Exeter, UK
⁴ Department of Psychology, Brown University, USA
⁵ Institute for Psychological Research, University of Leiden, The Netherlands

Key nodes within a fronto-basal ganglia network are increasingly engaged when one
anticipates the need for response inhibition. This finding suggests that an action plan
for stopping is proactively prepared even when there is no signal to stop. Previous
work has shown that the goal-oriented prefrontal cortex (PFC) commands the basal
ganglia to gate actions. However, little is known whether proactive preparation of
action plans helps reducing the role of top-down control in action selection. Here, we
tested the prediction that fronto-subcortical connections are modulated by the
advance preparation of action plans. Functional magnetic resonance imaging data
was collected while human participants performed a stop task with cues indicating
the likelihood of a stop-trial presentation. Effective connectivity analysis indicated that
the proactive engagement of the full stop network during go trials is adjusted to the
likelihood of stop trial occurrence. Importantly, when stopping was proactively
prepared, fronto-subcortical projections were weaker during actual stop-trials as
compared to reactive stop trials. When stop trials were salient and unprepared, the
genetic variability of the catechol-O-methyltransverase (COMT) gene was closely
related to individual differences in response regulation, inhibition, and fronto-
subthalamic connections. Together, findings from the present study suggest that the
level of advance preparation reduces the need for fronto-subcortical communication.
When stopping was unprepared, the level of dopamine in the PFC was closely
related to the efficiency of stopping and the strength of cortico-subthalamico
communications important for fast braking, or voluntary responses regulation.

Talk 4:

Dissociating action cancellation and action restraint – Evidence from prefrontal and basal ganglia lesion patients

Ulrike M. Krämer¹, Anne-Kristin Solbakk², Robert T. Knight^3
1 Dept. of Neurology, University of Lübeck, Germany
² Oslo University Hospital, Norway
³ Helen Wills Neuroscience Institute, University of California at Berkeley, USA

Research on inhibitory motor control has implicated several prefrontal as well as
subcortical and parietal regions in response inhibition. Whether prefrontal regions are
critical for inhibition, attention or task-set representation is still under debate. We
investigated the critical influence of the lateral PFC on response inhibition by using
cognitive electrophysiology in prefrontal lesion patients. Patients and controls did not
differ in their inhibitory speed (stop-signal and change-signal reaction time, SSRT
and CSRT), but patients made more errors in a Go/Nogo task and showed more
variable performance. These data stress the role of the PFC in maintaining inhibitory
control but not in actual inhibition supporting a dissociation between action
cancellation and PFC dependent action restraint. Laplacian transformed event-
related potentials (ERPs) revealed reduced parietal activity in PFC patients in
response to the stop-signals, and increased frontal activity over the intact
hemisphere. This electrophysiological finding supports altered PFC dependent visual
processing of the stop-signal in parietal areas and compensatory activity in the intact
frontal cortex. Interestingly, when administering the Go/Nogo and Stop-signal tasks in
a group of patients with unilateral basal ganglia lesions, we found evidence for a
dissociation in terms of behavioral impairments: PFC lesion patients made more
commission errors in the Go/Nogo task but had an average SSRT, whereas basal
ganglia patients showed a clearly increased SSRT but not more commission errors
than controls. I will discuss implications of these findings for current models of
response inhibition.