Demis Basso

TMS on Right Frontal Eye Fields Induces an Inflexible Focus of Attention

The focus of spatial attention can be not only oriented to a particular location, but also adjusted in its size to select visual information from a narrow (zoom-in) or broad (zoom-out) region of the visual field. Attentional orienting, saccades programming, and visual search have been linked to the frontal eye fields (FEF) activity. However, the FEF causal role in the frontoparietal network for the attentional focus size modulation remains unclear. Here, we delivered single-pulse transcranial magnetic stimulation (TMS) on FEF while participants performed an attentional zooming task. They were asked to detect a visual target appearing at 3 eccentricities from the fixation. Two cue types modulated the size of the attended region: a small cue was employed to narrow the attentional focus, whereas a large cue induced participants to broaden the attended region. Results showed that TMS delivered on the right FEF, but not on the left FEF, was able to interfere with both zoom-in and zoom-out attentional mechanisms. Our results provide the first evidence of the right FEF casual role in the attentional zooming control and give new insights into the neural mechanisms of dysfunctional spatial attention deployment shown in neurodevelopmental disorders, such as autism and dyslexia.

Low-frequency rTMS inhibitory effects in the primary motor cortex: Insights from TMS-evoked potentials

The neuromodulatory effects of repetitive transcranial magnetic stimulation (rTMS) have been mostly investigated by peripheral motor-evoked potentials (MEPs). New TMS-compatible EEG systems allow a direct investigation of the stimulation effects through the analysis of TMS-evoked potentials (TEPs). We investigated the effects of 1-Hz rTMS over the primary motor cortex (M1) of 15 healthy volunteers on TEP evoked by single pulse TMS over the same area. A second experiment in which rTMS was delivered over the primary visual cortex (V1) of 15 healthy volunteers was conducted to examine the spatial specificity of the effects. Single-pulse TMS evoked four main components: P30, N45, P60 and N100. M1-rTMS resulted in a significant decrease of MEP amplitude and in a significant increase of P60 and N100 amplitude. There was no effect after V1-rTMS. 1-Hz rTMS appears to increase the amount of inhibition following a TMS pulse, as demonstrated by the higher N100 and P60, which are thought to originate from GABAb-mediated inhibitory post-synaptic potentials. Our results confirm the reliability of the TMS-evoked N100 as a marker of cortical inhibition and provide insight into the neuromodulatory effects of 1-Hz rTMS. The present finding could be of relevance for therapeutic and diagnostic purposes.

Modulation of a fronto-parietal network in event-based prospective memory: an rTMS study.

Event-based prospective memory (PM) is a multi-component process that requires remembering the delayed execution of an intended action in response to a pre-specified PM cue, while being actively engaged in an ongoing task. Some neuroimaging studies have suggested that both prefrontal and parietal areas are involved in the maintenance and realization of delayed intentions. In the present study, transcranial magnetic stimulation (TMS) was used to investigate the causal involvement of frontal and parietal areas in different stages of the PM process (in particular, target checking and intention retrieval), and to determine the specific contribution of these regions to PM performance. Our results demonstrate that repetitive TMS (rTMS) interferes with prospective memory performance when applied at 150-350 ms to the right dorsolateral prefrontal cortex (DLPFC), and at 400-600 ms when applied to the left posterior parietal cortex (PPC). The present study provides clear evidence that the right DLPFC plays a crucial role in early components of the PM process (target checking), while the left PPC seems to be mainly involved in later processes, such as the retrieval of the intended action.

Touching Motion: rTMS on the Human Middle Temporal Complex Interferes with Tactile Speed Perception

Brain functional and psychophysical studies have clearly demonstrated that visual motion perception relies on the activity of the middle temporal complex (hMT+). However, recent studies have shown that hMT+ seems to be also activated during tactile motion perception, suggesting that this visual extrastriate area is involved in the processing and integration of motion, irrespective of the sensorial modality. In the present study, we used repetitive transcranial magnetic stimulation (rTMS) to assess whether hMT+ plays a causal role in tactile motion processing. Blindfolded participants detected changes in the speed of a grid of tactile moving points with their finger (i.e. tactile modality). The experiment included three different conditions: a control condition with no TMS and two TMS conditions, i.e. hMT+-rTMS and posterior parietal cortex (PPC)-rTMS. Accuracies were significantly impaired during hMT+-rTMS but not in the other two conditions (No-rTMS or PPC-rTMS), moreover, thresholds for detecting speed changes were significantly higher in the hMT+-rTMS with respect to the control TMS conditions. These findings provide stronger evidence that the activity of the hMT+ area is involved in tactile speed processing, which may be consistent with the hypothesis of a supramodal role for that cortical region in motion processing.

Planning, prospective memory, and decision-making: three challenges for hierarchical predictive processing models.

A commentary on Whatever next? Predictive brains, situated agents, and the future of cognitive science by Clark, A. (2012). Behav. Brain Sci. (in press). The present commentary on Clark (2012) will emphasize and discuss the role that high processing related to action planning may have in Bayesian predictive processing and will suggest possible directions for managing the issue. Clark agrees to define planning as follows: “we imagine a future goal state as actual, then use Bayesian inference to find the set of intermediate states (which can now themselves be whole actions) that get us there” (§ 1.5). Although this definition was reported to corroborate the unified vision of sensor processing, motor control, and planning suggested by Toussaint (2009), it does not correspond to the current representation of the planning process in two aspects. The first aspect entails the hierarchical vision of a plan as a succession of intermediate states. Research on planning (Basso et al., 2001; Phillips et al., 2001) has shown that the future goal state created in the beginning is accurate only in some particular circumstances (i.e., when both the task and algorithm are well-defined). In most cases, people are used to facing underspecified tasks in which a future goal state cannot be employed to derive the intermediate states (see Goel and Grafman, 2000). The first plan created is a general sketch of the intentions, a blurred image of the desired goal created by a feedforward prediction, which is successively refined through a continuous interaction between action and perception (Basso and Olivetti Belardinelli, 2006; Cisek, 2007). When the hierarchical predictive processing (HPP) presented by Clark is applied to the planning of motor sequences, it is undoubtedly convincing, as it explains the sensorimotor loop in an efficient way. However, the same mechanism may be too limited when applied to the planning of complex actions sequences. For example, in a planning task such as the Traveling Salesperson Problem (TSP: MacGregor and Ormerod, 1996), participants changed the initially planned strategy during task execution (Basso et al., 2006). Moreover, Cazzato et al. (2010) have demonstrated that a proficient performance is related to cognitive flexibility (shown while reconsidering the strategy chosen in the beginning) and not to the amount of information retrieved by ocular movements. That is, the overall organized behavior must be considered as more important than the summation of single actions. The second aspect entails the timing in which the plan and (sequence of) action(s) may occur. In a stimulus-response paradigm a plan is created and promptly used because the action must be implemented as soon as possible. However, in many real-world situations, events develop in time and the planned actions must be postponed in order to be executed at the appropriate moment. Garling (1994) has provided an example of everyday planning using a fictitious environment in which participants must organize a trip through several errands like stores with different opening hours. This delay between the plan and its implementation is also shared with other cognitive processes such as prospective memory (PM: Kliegel et al., 2008). PM requires that a planned action should be executed only whenever the circumstances fulfill the conditions, which were commonly not present when the plan was created. In a standard scenario, a plan should be kept in mind while a person is involved in other ongoing activities, until the activating conditions are satisfied. At that moment, the person should inhibit the ongoing activity, switch to the prospective activity, and execute the plan. During the ongoing activity, some lure stimuli (distracters, see for PM: Bisiacchi et al., 2011) could share certain commonalities with the activating cues, but not enough to satisfy all the conditions. In these cases, according to HPP, the prospective action would increase its activation value and the probability of being executed as well, whereas it should be inhibited instead. HPP models are also required to account for the inhibition generated by long-lasting intentions. In the present state of the art, HPP-based models are outstanding in producing a response to a stimulus, but this response is locked in time to the stimulus itself (i.e., it is simultaneous to or must follow the stimulus as closely as possible). Providing explanations also for the realization of plans with delayed actions would be a good benchmark for determining the effective legitimacy of Clarks approach. One attempt of this kind has been proposed by Shadlen et al. (2008) in decision-making. According to their accumulator model, decisions are taken when the accumulated evidence promoting a specific choice exceeds a certain threshold value (determined by prior information and costs). Abstract decisions (i.e., those producing a plan) are essentially aimed at creating rules instead of actions. It is important to highlight that, with respect to Clarks model, Shadlens includes some components of the Bayesian inference, but it avoids using its major assumption, the posterior probability. Higher processing falls beyond the aim of Clarks target article, but it is central in its relevance for a model aiming at describing human processing. It is not that motor planning is more or less important than other higher-level planning, but they both show the same level of importance and need to be explained. A unified mechanism for managing input–output processes is undoubtedly efficient and successful in species evolution. Therefore, it is likely that it is shared with many animals, too. However, since human beings have developed more complex behaviors and processes with respect to those managed by other animals, HPP must be shown to be flexible enough to (1) manage high levels of information (if it is the only mechanism), or (2) collaborate with other mechanisms of information processing. Clark is aware of this possible limitation, as he posed it in terms of open questions. The mechanism of predictive processing could be sufficiently powerful to be successfully applied to higher processing, as suggested by Cisek and Kalaska (2010, p. 276) too, but large-scale non-hierarchical mechanisms (able to recursively manage several processing systems) must also be hypothesized. Evidence from neuroscience enlightened that magnetic stimulation produces different effects, which are dependent on initial conditions of the cell assembly (Hoshi et al., 2000; Silvanto et al., 2008). State-dependent cell assemblies provide the cognitive system with flexibility that is likely to account for high-level (long-term) processes such as planning, PM, and decision-making.

Transcranial Magnetic Stimulation and Neuroimaging Coregistration

The development of neuroimaging techniques is one of the most impressive advancements in neuroscience. The main reason for the widespread use of these instruments lies in their capacity to provide an accurate description of neural activity during a cognitive process or during rest. This important advancement is related to the possibility to selectively detect changes of neuronal activity in space and time by means of different biological markers. Specifically, functional magnetic resonance imaging (fMRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), and nearinfrared spectroscopy (NIRS) use metabolic markers of ongoing neuronal activity to provide an accurate description of the activation of specific brain areas with high spatial resolution. Similarly, electroencephalography (EEG) is able to detect electric markers of neuronal activity, providing an accurate description of brain activation with high temporal resolution. The application of these techniques during a cognitive task allows important inferences regarding the relation between the detected neural activity, the cognitive process involved in an ongoing task, and behaviour: this is known as a “correlational approach”.

Consciousness, not only intentionality, yields self-harming behavior

As pointed out by Searle (1987), sub-jectivity and intentionality have alwaysbeen defined as basic characteristics ofconsciousness. Both of them are alsoneeded in order to determine whethera person is a (self-)murderer or not: alegal report of the consciousness stateshould verify whether at that particularmoment a person was subjectively andintentionally able to decide on his/herown actions. Despite the relevance of thisassessment, at the moment the scien-tific community is not providing a uni-fied definition of consciousness (Velmans,2009). This lack is particularly relevantfor psychopathology, since consciousnessproblems have been connected to sev-eral clinical pathologies. In the past, veryscarce attention has been paid to theclinical assessment of consciousness, andresearch was mainly devoted to disordersof consciousness. However, assessment ofconsciousness has been acknowledged asbeing extremely relevant for psychiatricpathologies too, as a way of prevent-ing self-harming and suicidal behavior.Several pathologies could result in suici-dal behavior, such as schizophrenia (Boband Mashour, 2011), substance-relateddisorders (Bortelote et al., 2004), post-traumatic stress disorder (O’Brien andNutt, 1998), eating disorders (Favaro andSantonastaso,1995),andothers.Literaturehas usually divided people linked toself-harm into two branches: those whocommitted suicidal actions with a specificintention (intentional suicides, ISP), andthose who died as a consequence of a riskybehavior,withoutaclearsuicidalintention(risky behavior people, RBP).The ISP sample is mainly composedby people who are/were suffering fromeither major or mixed depressive episodes(Schneider, 2003; Bortelote et al., 2004).These patients usually focus attention onsingle aspects of their perception, con-cerning inner experiences (Ringel, 1953)or circumstances (i.e., confrontation withlifeortraumaticeventsaswellasdevel-opmental tasks: Tschiesner et al., 2012).Patients of this group perceive and elab-orate only specific contents according totheir symptoms, and this may be viewedalso as a restriction of consciousness(Ringel, 1953; Poldinger, 1968). The con-tent of their phenomenal consciousnessconsists, on the one hand, mainly of emo-tional experiences in many cases ratedmore intense as normal, and, on the otherhand, of a constriction in perceiving alter-native ways of behavior or reaction indifficult situations. Therefore, a dyspho-ric mood characterizes consciousness andtriggers intentions of the same conno-tation, forcing people to direct aggres-sion toward themselves (Ringel, 1953).Rottenberg et al. (2006) have shown thiscongruency between mood and behaviorin depressive patients, a fact that, in turn,wouldexplain whyitissodifficult todefertheir attention from their negative emo-tional status, which could lead them tocarry out suicidal actions. Self-harmingbehavioristhereforeoneoftheaimsofISP,and consistent with, and caused by, theirconstricted consciousness.The RBP category includes people thatare for example looking for thrills doingextreme sports or putting themselvesin dangerous situations, or doing theirofficial jobs like policemen, paramedics,soldiers,orfirefighters(Goma-i-Freixanet,1995; Tschiesner, 2012). The drive forsituations characterized by novelty andintensity has been described in theSensations Seeking sub-construct “thrilland adventure seeking” (Zuckerman,2007). Sensation-seekers are described asshowingalowlevelofarousal,andtheytryto increase it, in an unconscious way, bydoing extreme sports, consuming drugs,attending religious rituals and so on.This way of controlling arousal throughintense and novel stimuli (Arnett, 1995;Zuckerman, 2007) has been indicated asthe main indirect cause for assuming risksand provoking accidents. Accordingly,Schneider and Rheinberg (2003) arguedthat the aim of risky behavior—by doingrisky activities–is not the danger in itself,but the ability to keep control in dan-gerous situations. Keeping control in adesperate situation like climbing a wallwithout a rope is linked with pleasure(Balint, 1959). Rephrasing, we may saythat RBP seek to manage themselves inextreme situations, in which normal peo-plewouldn’tbeabletodoso.Thisway,RBP are intentionally targeting on theperformance but not the correlated risks,the latter being part of the whole situa-tion,butexcludedfromconsciousanalysis.The access to consciousness is influenced