Movement, mood and cognition: Preliminary insights into the therapeutic effects of electroconvulsive therapy for depression through a resting-state connectivity analysis

BACKGROUND

Electroconvulsive therapy (ECT) is a highly effective treatment for depression but how it achieves its clinical effects remains unclear.

METHODS

We set out to study the brain's response to ECT from a large-scale brain-network perspective. Using a voxelwise analysis, we looked at resting-state functional connectivity before and after a course of ECT at the whole-brain and the between- and within-network levels in 17 patients with a depressive episode. Using a group-independent component analysis approach, we focused on four networks known to be affected in depression: the salience network (SN), the default mode network (DMN), the cognitive executive network (CEN), and a subcortical network (SCN). Our clinical measures included mood, cognition, and psychomotor symptoms.

RESULTS

We found ECT to have increased the connectivity of the left CEN with the left angular gyrus and left middle frontal gyrus as well as its within-network connectivity. Both the right CEN and the SCN showed increased connectivity with the precuneus and the anterior DMN with the left amygdala. Finally, improvement of psychomotor retardation was positively correlated with an increase of within-posterior DMN connectivity.

LIMITATIONS

The limitations of our study include its small sample size and the lack of a control dataset to confirm our findings.

CONCLUSION

Our voxelwise data demonstrate that ECT induces a significant increase of connectivity across the whole brain and at the within-network level. Furthermore, we provide the first evidence on the association between an increase of within-posterior DMN connectivity and an improvement of psychomotor retardation, a core symptom of depression.

Toward Targeted ECT: The Interdependence of Predictors of Treatment Response in Depression Further Explained

OBJECTIVE

Several clinical variables assumed to be predictive of electroconvulsive therapy (ECT) outcome in major depressive disorder show substantial interrelations. The current study tries to disentangle this interdependence to distill the most important predictors of treatment success to help improve patient-treatment matching.

METHODS

We constructed a conceptual framework of interdependence capturing age, episode duration, and treatment resistance, all variables associated with ECT outcome, and the clinical symptoms of what we coin core depression, ie, depression with psychomotor agitation, retardation, psychotic features, or a combination of the three. The model was validated in a sample of 73 patients with a major depressive episode according to DSM-5 treated twice weekly with ECT (August 2015-January 2018) using path analyses, with the size and direction of all direct and indirect paths being estimated using structural equation modeling. Reduction in Montgomery-Asberg Depression Rating Scale (MADRS) scores during treatment was the ECT outcome measure.

RESULTS

The baseline presence of psychomotor agitation, retardation, and/or psychotic symptoms strongly correlated with beneficial ECT outcome (z = 0.84 [SE = 0.17]; P < .001), and the association between age and the effect of ECT appears to be mediated by their presence (z = 0.53 [SE = 0.18]; P = .004). There was no direct correlation between age and ECT response (P = .479), but there was for episode duration and ECT outcome (z = -0.38 [SE = 0.08]; P < .001).

CONCLUSIONS

ECT is a very effective treatment option for severe depressive disorder, especially for patients suffering from severe depression characterized by the presence of psychomotor agitation, psychomotor retardation, psychotic symptoms, or a combination of these 3 features, with the chance of a beneficial outcome being reduced in patients with a longer episode duration. Age may heretofore have been given too much weight in ECT decision making.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02562846.

Task intentions and their implementation into actions: cognitive control from adolescence to middle adulthood

Cognitive control processes involved in human multitasking arise, mature, and decline across age. This study investigated how age modulates cognitive control at two different levels: the level of task intentions and the level of the implementation of intentions into the corresponding actions. We were particularly interested in specifying maturation of voluntary task choice (intentions) and task-switching execution (their implementations) between adolescence and middle adulthood. Seventy-four participants were assigned to one of the four age groups (adolescents, 12-17 years; emerging adults, 18-22 years; young adults, 23-27 years; middle-aged adults, 28-56 years). Participants chose between two simple cognitive tasks at the beginning of each trial before pressing a spacebar to indicate that the task choice was made. Next, a stimulus was presented in one of the three adjacent boxes, with participants identifying either the location or the shape of the stimulus, depending on their task choice. This voluntary task-switching paradigm allowed us to investigate the intentional component (task choice) separately from its implementation (task execution). Although all participants showed a tendency to repeat tasks more often than switching between them, this repetition bias was significantly stronger in adolescents than in any adult group. Furthermore, participants generally responded slower after task switches than after task repetitions. This switch cost was similar across tasks in the two younger groups but larger for the shape than the location task in the two older groups. Together, our results demonstrate that both task intentions and their implementation into actions differ across age in quite specific ways.

Understanding Behavioural Rigidity in Autism Spectrum Conditions: The Role of Intentional Control

Although behavioural rigidity belongs to the core symptoms of autism spectrum conditions, little is known about its underlying cognitive mechanisms. The current study investigated the role of intentional control mechanisms in behavioural rigidity in autism. Autistic individuals and their matched controls were instructed to repeatedly choose between two simple cognitive tasks and to respond accordingly to the subsequently presented stimulus. Results showed that autistic participants chose to repeat tasks more often than their controls and when choosing to switch, they demonstrated larger performance costs. These findings illustrate that when required to make their own choices, autistic people demonstrate rigidity at different performance levels, suggesting that intentional control mechanisms might be important for a better understanding of behavioural rigidity in autism.

Cognitive control of intentions for voluntary actions in individuals with a high level of autistic traits

Impairments in cognitive control generating deviant adaptive cognition have been proposed to account for the strong preference for repetitive behavior in autism. We examined if this preference reflects intentional deficits rather than problems in task execution in the broader autism phenotype using the Autism-Spectrum Quotient (AQ). Participants chose between two tasks differing in their relative strength by indicating first their voluntary task choice and then responding to the subsequently presented stimulus. We observed a stronger repetition bias for the harder task in high AQ participants, with no other differences between the two groups. These findings indicate that the interference between competing tasks significantly contributes to repetitive behavior in autism by modulating the formation of task intentions when choosing tasks voluntarily.

Reduced accuracy and sensitivity in the perception of emotional facial expressions in individuals with high autism spectrum traits

Autism spectrum disorder (ASD) is among other things characterized by specific impairments in emotion processing. It is not clear, however, to what extent the typical decline in affective functioning is related to the specific autistic traits. We employed The Autism Spectrum-Quotient (AQ) to quantify autistic traits in a group of 500 healthy individuals and investigate whether we could detect similar difficulties in the perception of emotional expressions in a broader autistic phenotype. The group with high AQ score was less accurate and needed higher emotional content to recognize emotions of anger, disgust, and sadness. Our findings demonstrate a selective impairment in identification of emotional facial expressions in healthy individuals that is primarily related to the extent of autistic traits.

Perceptual wholes can reduce the conscious accessibility of their parts

Humans can rapidly extract object and category information from an image despite surprising limitations in detecting changes to the individual parts of that image. In this article we provide evidence that the construction of a perceptual whole, or Gestalt, reduces awareness of changes to the parts of this object. This result suggests that the rapid extraction of a perceptual Gestalt, and the inaccessibility of the parts that make up that Gestalt, may in fact reflect two sides of the same coin whereby human vision provides only the most useful level of abstraction to conscious awareness.

Integrating biological motion: the role of grouping in the perception of point-light actions

The human visual system is highly sensitive to biological motion and manages to organize even a highly reduced point-light stimulus into a vivid percept of human action. The current study investigated to what extent the origin of this saliency of point-light displays is related to its intrinsic Gestalt qualities. In particular, we studied whether biological motion perception is facilitated when the elements can be grouped according to good continuation and similarity as Gestalt principles of perceptual organization. We found that both grouping principles enhanced biological motion perception but their effects differed when stimuli were inverted. These results provide evidence that Gestalt principles of good continuity and similarity also apply to more complex and dynamic meaningful stimuli.

Collision judgment of objects approaching the head

Recent investigations have indicated that human perception of the trajectory of objects approaching in the horizontal plane is precise but biased away from straight ahead. This is remarkable because it could mean that subjects perceive objects that approach on a collision course as missing the head. Approach within the horizontal plane through the eyes and the fixation point (the plane of regard) is special, as general motions will also have a component of motion perpendicular to the plane of regard. Thus, we investigated three-dimensional motion perception in the vicinity of the head, including vertical components. Subjects judged whether an object that moved in the mid-sagittal plane was going to hit below or above a well-known reference point on the face like the center of the chin or the forehead (perceptual task). Tactile and proprioceptive information about the reference point significantly improved precision. Precision did not change with distance of the approaching target or with fixation direction. Bias was virtually absent for these vertical motions. When subjects pointed with their index finger to the perceived location of impact on their face (visuo-motor task), they overestimated (1.7 cm) the horizontal eccentricity of the point of impact (pointing task). Vertical bias, however, was again virtually absent. Interestingly, when trajectories intersected the plane of regard, higher precision was observed in the perceptual task regardless of the other conditions. In contrast, neither bias nor precision of the pointing task changed significantly when the trajectories intersected the plane of regard. When asked to point to the location where a trajectory intersected the plane of regard, subjects overestimated the depth component of this intersection location by about 3 cm. The absence of perceptual and pointing bias in the vertical direction in contrast to the clear horizontal bias suggests that different (combinations of) cues are used to judge these components of the trajectory of an approaching object. The results of our perceptual task suggest a role for somatosensory signals in the visual judgment of impending impact.

Perceptual compensation for eye torsion

To correctly perceive visual directions relative to the head, one needs to compensate for the eye's orientation in the head. In this study we focus on compensation for the eye's torsion regarding objects that contain the line of sight and objects that do not pass through the fixation point. Subjects judged the location of flashed probe points relative to their binocular plane of regard, the mid-sagittal or the transverse plane of the head, while fixating straight ahead, right upward, or right downward at 30 cm distance, to evoke eye torsion according to Listing's law. In addition, we investigated the effects of head-tilt and monocular versus binocular viewing. Flashed probe points were correctly localized in the plane of regard irrespective of eccentric viewing, head-tilt, and monocular or binocular vision in nearly all subjects and conditions. Thus, eye torsion that varied by +/-9 degrees across these different conditions was in general compensated for. However, the position of probes relative to the midsagittal or the transverse plane, both true head-fixed planes, was misjudged. We conclude that judgment of the orientation of the plane of regard, a plane that contains the line of sight, is veridical, indicating accurate compensation for actual eye torsion. However, when judgment has to be made of a head-fixed plane that is offset with respect to the line of sight, eye torsion that accompanies that eye orientation appears not to be taken into account correctly.

Localization of the plane of regard in space

When we fixate an object in space, the rotation centers of the eyes, together with the object, define a plane of regard. People perceive the elevation of objects relative to this plane accurately, irrespective of eye or head orientation (Poljac et al. (2004) Vision Res, in press). Yet, to create a correct representation of objects in space, the orientation of the plane of regard in space is required. Subjects pointed along an eccentric vertical line on a touch screen to the location where their plane of regard intersected the touch screen positioned on their right. The distance of the vertical line to the subject's eyes varied from 10 to 40 cm. Subjects were sitting upright and fixating one of the nine randomly presented directions ranging from 20 degrees left and down to 20 degrees right and up relative to their straight ahead. The eccentricity of fixations relative to the pointing location varied by up to 40 degrees . Subjects underestimated the elevation of their plane of regard (on average by 3.69 cm, SD=1.44 cm), regardless of the fixation direction or pointing distance. However, when the targets were shown on a display mounted in a table, to provide support of the subject's hand throughout the trial, subjects pointed accurately (average error 0.3 cm, SD=0.8 cm). In addition, head tilt 20 degrees to the left or right did not cause any change in accuracy. The bias observed in the first task could be caused by maintained tonus in arm muscles when the arm is raised, that might interfere with the transformation from visual to motor signals needed to perform the pointing movement. We conclude that the plane of regard is correctly localized in space. This may be a good starting point for representing objects in head-centric coordinates.

Representation of heading direction in far and near head space

Manipulation of objects around the head requires an accurate and stable internal representation of their locations in space, also during movements such as that of the eye or head. For far space, the representation of visual stimuli for goal-directed arm movements relies on retinal updating, if eye movements are involved. Recent neurophysiological studies led us to infer that a transformation of visual space from retinocentric to a head-centric representation may be involved for visual objects in close proximity to the head. The first aim of this study was to investigate if there is indeed such a representation for remembered visual targets of goal-directed arm movements. Participants had to point toward an initially foveated central target after an intervening saccade. Participants made errors that reflect a bias in the visuomotor transformation that depends on eye displacement rather than any head-centred variable. The second issue addressed was if pointing toward the centre of a wide-field expanding motion pattern involves a retinal updating mechanism or a transformation to a head-centric map and if that process is distance dependent. The same pattern of pointing errors in relation to gaze displacement was found independent of depth. We conclude that for goal-directed arm movements, representation of the remembered visual targets is updated in a retinal frame, a mechanism that is actively used regardless of target distance, stimulus characteristics or the requirements of the task.