Is cognitive control automatic? New insights from transcranial magnetic stimulation.

Cognitive control has been classically considered as a flexible process engaged to pursue intentional behaviors, as distinct from automatic processes, which are unintentional, inflexible, and triggered by unconscious mechanisms. Our study challenged this view, showing that such a distinction may not be so clear-cut. We analyzed motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation to investigate the neurocognitive mechanisms occurring in a conflict task during trials that either required or did not require a response. We observed a Simon effect on MEPs and sequential modulations of such effects on both kinds of trials. Sequential modulations are usually explained as resulting from the engagement of intentional control mechanisms. Our findings rule against this idea, suggesting that these effects are the result of a mechanism that detects and resolves conflict even when there is no intention to select any response. Accordingly, cognitive control also seems to operate without intention, acting in an automatic fashion.

Computer-based attention-demanding testing unveils severe neglect in apparently intact patients.

We tested a group of ten post-acute right-hemisphere damaged patients. Patients had no neglect according to paper-and-pencil cancellation tasks. They were administered computer-based single- and dual-tasks, requiring to orally name the position of appearance (e.g. left vs. right) of briefly-presented lateralized targets. Patients omitted a consistent number of contralesional targets (≈ 40%) under the single-task condition. When required to perform a concurrent task which recruited additional attentional resources (dual-tasks), patients' awareness for contralesional hemispace was severely affected, with less than one third of contralesional targets detected (≈ 70% of omissions). In contrast, performance for ipsilesional (right-sided) targets was close to ceiling, showing that the deficit unveiled by computer-based testing selectively affected the contralesional hemispace. We conclude that computer-based, attention-demanding tasks are strikingly more sensitive than cancellation tasks in detecting neglect, because they are relatively immune to compensatory strategies that are often deployed by post-acute patients.

Reasons for holding a Consensus Conference on neuropsychological rehabilitation in adult patients.

Neuropsychological deficits are common in various cerebrovascular, neurodegenerative and traumatic pathologies. Neuropsychological rehabilitation refers to a set of interventions that aim to improve a person's ability to perform cognitive tasks by retraining previously learned skills and teaching compensatory strategies. However, today there are some relevant points that need of further investigations. In 2007, a Task Force was set up under the auspices of several scientific societies that operate in the field of psychology, neuropsychology, rehabilitation and neurology (AIP, GIRN, SIMFER, SIN, SINP, and SPAN) with the aim to clarify the theoretical background of neuropsychological rehabilitation and to assess the diagnostic instruments and the treatments available to date. This consensus conference (CC), using methods derived from those of Evidence-Based-Medicine (EMB), evaluated several points, including: a) legal aspects; b) epidemiological aspects; c) neuropsychological rehabilitation of attentional and executive disorders; d) neuropsychological rehabilitation of speech/language disorders; e) neuropsychological rehabilitation of visual field defects; f) neuropsychological rehabilitation of neglect; g) neuropsychological rehabilitation of memory disorders; h) cognitive rehabilitation of arm apraxia; i) neuropsychological rehabilitation of Alzheimer disease; j) rehabilitation of multiple sclerosis; k) rehabilitation of severe brain injuries; l) rehabilitation of mild to moderate brain injuries; m) rehabilitation of behavioral disorders in severe brain injuries. Then, CC submitted to a specific Jury a final report with summary tables and questions. The final meeting of the Jury was held in Siena in February 2010.

Global/local processing and negative priming: the influence of selection difficulty and stimulus exposure.

Negative priming is a decrement in performance observed when a previously ignored stimulus is re-presented as a target. The present study examined the relation between selection difficulty and negative priming in five experiments that used hierarchical stimuli (large letters made up by small letters). The results show that negative priming is greater when subjects direct attention to the local level (more difficult selection) than when they direct attention to the global level (less difficult selection). However, that occurs only when exposure of prime and probe is sufficiently long. With shorter presentations, negative priming is still observed but is no longer modulated by selection difficulty. These results suggest that both anticipatory and reactive mechanisms are responsible for the occurrence of negative priming and that instantiation of the reactive mechanism depends on the time available for prime and probe selection.

Focusing attention on overlapping and non-overlapping figures with subjective contours.

In a series of five experiments we investigated whether observers could focus attention on a restricted visual area that was demarcated by Kanizsa-like subjective contours, and whether this effect also occurred in the case of overlapping figures. The task was a simple reaction time to a luminance increment and the basic finding was that reaction time was faster when the imperative stimulus fell inside the focus of attention than when it fell outside. The first two experiments showed that the extent of the attentional focus could be adapted to a region that was demarcated by subjective contours, thus extending the results of previous studies that used regions demarcated by real contours. The last three experiments showed that, regardless of the type of margins, focusing was more efficient for the figure that was perceived as lying in front in a pair of overlapping figures.

Cortical plasticity of spatial stimulus-response associations: electrophysiological and behavioral evidence.

Right-handed subjects tend to respond faster to stimuli presented in the visual hemifield that spatially corresponds to the responding hand. In a typical Simon task, response is based on a non-spatial salient feature of the stimulus (e.g. color) whereas its position must be ignored. However, the spatial position of the stimulus interferes with the processing of the salient characteristic. Subjects are significantly faster when stimulus side and response side correspond (corresponding condition) than when they do not (non-corresponding condition). We have previously shown with behavioral experiments that, when subjects practice reversed contingencies (that is, spatially incompatible trials) in a session preceding the Simon task, they show a long-term retention of these associations, resulting in the disappearance of the latency cost typically observed in non-corresponding trials. Here we show, by means of the lateralized readiness potential, that the neural correlate of such behavioral plasticity is an increase in premotor cortex activation during preparation of non-corresponding responses. This effect showed a marked left-right asymmetry which suggests an important role of subjects' handedness. Our results demonstrate that humans can learn in a single session to reverse relatively stable stimulus-response associations.

Shifting attention between objects.

Experiment 1 used a modified spatial cueing paradigm that was introduced by Egly et al. [J. Exp. Psychol. Gen. 123 (1994) 161] to investigate the cost incurred in shifting attention within an object as opposed to shifting attention between objects. Subjects were presented with two outline rectangles and had to detect a target (a luminance increment) that could appear in the cued location (valid trials), in an uncued location inside the cued rectangle (inside-invalid trials), or in an uncued location inside the uncued rectangle (outside-invalid trials). Valid trials were faster than invalid trials, and inside-invalid trials were faster than outside-invalid trials. In Experiment 2, the two rectangles were joined to form a unitary object. Here, no difference was found between outside-invalid trials and inside-invalid trials. Experiment 3 showed that the delayed response on outside-invalid trials in Experiment 1 was not due to attention needing to cross the figural borders in order to re-orient to the uncued rectangle. The results were interpreted as showing that an extra cost is incurred for shifting attention between different objects.

Shifting visuo-spatial attention in a virtual three-dimensional space.

The present investigation, with a virtual reality set-up, aimed to study attentional orienting within a three-dimensional visual world. Near and far stimuli were used. Half of the subjects were provided with a virtual representation of their body, whereas half were not. Results showed a different distribution of attentional resources in the two conditions, suggesting a dissociation between attentional systems controlling the proximal and the distal visual space. In particular, attention was focused close to the subject's body when a virtual representation of it was present, whereas attention was focused away from the body when a virtual representation of the body was not present.

Modulation of inhibition of return by type and number of dynamic changes of the cue.

Inhibition of return (IOR) is a response delay when the target is preceded by an irrelevant stimulus (cue) at the same location. In a previous study, we investigated the separate and joint effects on IOR of cue onset and offset. IOR was much greater when cue onset was followed by cue offset (on-off cue) than when the cue was a single event (on or off cues). The aim of the present study was to test whether the greater IOR with an on-off cue is due to the presence of two cue events. Three experiments were conducted. In Experiment 1 we replicated, with a different delay between cue onset and offset, the finding that IOR is greater with an on-off cue than with a single cue event. In Experiments 2 and 3, we used cues formed by two events. In Experiment 2, an on-off cue was compared with an off-on cue, whereas in Experiment 3 an on-on cue was compared with an off-off cue. Results showed that the magnitude of IOR did not simply depend on the number of cue events occurring before the target. IOR was greater with two different events than with two identical events and greater when was preceded by an off-event than an on-event. Therefore, IOR was greatest with an on-off cue, which likely also benefited from a gap effect. Possible mechanisms underlying IOR were discussed.

Automatic and voluntary focusing of attention.

In this study, we investigate whether attentional focusing, like attentional orienting, comprises two independent mechanisms. We provide direct empirical evidence in favor of the existence of two mechanisms--one exogenous, or automatic, and one endogenous, or voluntary--that play a role in adjusting the size of the focus of attention. When a new object suddenly occurs in the visual field, the focus is first automatically fitted to it, and then an endogenous effort has to be exerted to maintain attention in the focused mode. Also, we provide evidence that voluntary focusing needs a perceptual object in order to operate.

Rehabilitation of executive deficits in closed head injury and anterior communicating artery aneurysm patients.

This paper reports a study that was aimed to rehabilitate executive functions in closed head injury (CHI) and anterior communicating artery (ACoA) aneurysm patients. The groups tested comprised 10 CHI patients, 9 ACoA aneurysm patients and 19 controls. We employed a dual-task paradigm that is known to tap the ability to co-ordinate two actions. The treatment consisted of five experimental sessions, in which the dual-task paradigm was used. In the CHI study, the dual-task cost was measured before the treatment (assessment), immediately after the treatment (retest), and 3 months after the treatment (follow-up). In the ACoA aneurysm study, the dual-task cost was also assessed 12 months after the treatment. A significant reduction of the dual-task cost from assessment to retest was found. This reduction remained stable in the follow-up sessions. The results are discussed with reference to the absence of spontaneous recovery of this specific executive function and to the possibility that the beneficial effect of the treatment generalises to other executive functions and/or daily living activities.

Response strategies and the Simon effect.

The study investigated whether the Simon effect, and its facilitation and interference components, shows up in reaction time (RT) or in movement time (MT), depending on the response strategy. Experiment 1 replicated a study by Hietanen and Rämä. Subjects had to press one of two lateralised keys in response to one of two stimuli. The stimuli were presented in the center (neutral condition) or to the left or right side (corresponding or non-corresponding conditions). To press the response key, a reaching movement was necessary, and both RT and MT were recorded. One group of subjects showed an RT facilitation effect and an MT interference effect. Another group of subjects showed both MT facilitation and MT interference effects. It was hypothesized that the two groups used different response strategies. In Exps. 2 and 3, the subjects were explicitly instructed to use the two strategies that were hypothesized for Exp. 1. The results showed that whether facilitation and interference manifest themselves in RT or MT depends on the response strategy adopted by the subjects.

How to avoid the fallacies of cognitive subtraction in brain imaging.

Functional neuroanatomy of cognitive processes is generally derived by subtraction of a control task from an experimental task. We show that this method is logically untenable and propose to replace it with an adaptation of the specific-effect method and of the additive-factor method. The basic flaw that undermines the subtractive method is the comparison between different tasks. We argue that the specific-effect method should be used when investigating activations produced by different levels of a qualitative variable, whereas the additive-factor method should be used for quantitative variables. The use of these methods allows one to distinguish between parallel and serial stages of processing and between local and distributed processing.

Configural processing at birth: evidence for perceptual organisation.

We report a series of ten experiments aimed to investigate the newborn's ability to discriminate the components of a visual pattern and to process the visual information that specifies the global configuration of a stimulus. The results reveal that: (i) newborn babies are able to distinguish individual elements of a stimulus (experiments 1A, 1B, 1C, and 1D); (ii) they can group individual elements into a holistic percept on the basis of Gestalt principles (experiments 2A and 3A); (iii) their spontaneous preferences cannot be easily modified by habituation (experiments 2B and 3B); and (iv) when horizontal stimuli are paired with vertical stimuli, they prefer the horizontal ones (experiments 4A and 4B).

The role of long-term-memory and short-term-memory links in the Simon effect.

In Experiment 1, children performed a Simon task after a spatially compatible or incompatible task. Results showed a Simon effect after the spatially compatible task and a reversed Simon effect after the spatially incompatible task. In Experiments 2-5, an identical procedure was adopted with adult participants, who performed the Simon task immediately after, a day after, or a week after the spatial compatibility task. Experiment 6 established a baseline for the Simon effect. Results showed a Simon effect after the spatially compatible task and no Simon effect or a reversed Simon effect after the spatially incompatible task. A modified version of the computational model of M. Zorzi and C. Umiltà (1995) was used to compare possible accounts of the findings. The best account exploits 2 types of short-term-memory links between stimulus and response and their interaction with long-term-memory links.

Visuospatial attention in myopia.

Four experiments were conducted to ascertain whether myopia is associated with deficits of visuospatial attention. In myopic and emmetropic control subjects, we studied: (1) automatic and voluntary orienting of attention, (2) focusing of attention and (3) performance on a visual search task. The results indicated that automatic orienting was defective in myopics and their performance in visual search was less efficient than that of controls. By contrast, myopics showed no deficits in voluntary orienting and in focusing.

Facilitation and interference components in the Simon effect.

In four experiments we investigated whether the Simon effect consists of both facilitation and interference. In Experiment 1 subjects had to press one of two lateralized keys in response to one of two stimuli (a rectangle or a square). The stimuli were presented at fixation or to the right or left of it. The stimulus-response mappings could be corresponding (i.e., right key--rectangle or square on the right side), non-corresponding (i.e., right key--rectangle or square on the left side), or neutral (i.e., stimulus in the center). Results showed both facilitation and interference effects, but interference was three times greater than facilitation. To test whether the neutral position was favored by visual acuity, Experiments 2, 3 and 4 used slight different displays where visual acuity was the same at every stimulus position. Results indicated that the Simon effect is comprised of facilitation and interference components of the same magnitude. These findings were discussed with reference to dual-route models of the Simon effect.

Somatosensory extinction for meaningful objects in a patient with right hemispheric stroke.

Implicit, high level processing of extinguished objects has often been described in the visual modality. In the tactile domain, however, research on this topic is meagre and it is still uncertain whether processing of tactually presented stimuli can be affected by the same attentional disorders as visual stimuli. In this paper we describe a patient, ENM, with visual neglect and light touch extinction who, in a naming task of objects presented in the tactile modality, simultaneously to both hands, showed extinction for left hand objects. He was, nevertheless, able to make above chance Same/Different judgements on the two stimuli. We also tested two neurologically intact subjects who performed the test wearing a ski-glove on the left hand to impair the recognition of left hand objects. In these subjects, Same/Different judgements were at chance level when recognition rate was as low as that found in patient ENM. This happened when either the objects, although sharing the same name were different in shape (conditions Same-Different) or when the two objects were different with respect to the category name but were actually physically similar (conditions Different-Similar). However, when the objects were either identical or completely different, i.e., in a condition where judgement could be based simply on the physical analysis of the object shape (condition Same Identical and Different Dissimilar), their Same/Different judgements were above chance, despite the tactual deficit. Our conclusion was that patient ENM showed implicit recognition of left hand objects, at least in the Same Different and in the Different-Similar conditions, whereas, in the same conditions, normal subjects with an artificial sensory impairment did not. Our results also show that Same/Different judgements may be, in some conditions, less demanding than naming tasks, as suggested by Farah et al. Furthermore, patient ENM performed the test both with uncrossed and crossed hands. We found that extinction always affected the hand contralateral to the brain damage, although there was a tendency for a decrement of the ipsilesional hand performance in the crossed condition. We discuss these findings with reference to the most recent theories on the existence of a body centered spatial frame of reference.