Sara Agosta

How to Accurately Detect Autobiographical Events

We describe a new method, based on indirect measures of implicit autobiographical memory, that allows evaluation of which of two contrasting autobiographical events (e.g., crimes) is true for a given individual. Participants were requested to classify sentences describing possible autobiographical events by pressing one of two response keys. Responses were faster when sentences related to truly autobiographical events shared the same response key with other sentences reporting true events and slower when sentences related to truly autobiographical events shared the same response key with sentences reporting false events. This method has possible application in forensic settings and as a lie-detection technique.

Modulation of smoking and decision-making behaviors with transcranial direct current stimulation in tobacco smokers: a preliminary study

BACKGROUND Most tobacco smokers who wish to quit fail to reach their goal. One important, insufficiently emphasized aspect of addiction relates to the decision-making system, often characterized by dysfunctional cognitive control and a powerful drive for reward. Recent proof-of-principle studies indicate that transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) can transiently modulate processes involved in decision-making, and reduce substance intake and craving for various addictions. We previously proposed that this beneficial effect of stimulation for reducing addictive behaviors is in part mediated by more reflective decision-making. The goal of this study was to test whether nicotine intake and decision-making behaviors are modulated by tDCS over the DLPFC in tobacco smokers who wished to quit smoking. METHODS Subjects received two five-day tDCS regimens (active or sham). Stimulation was delivered over the right DLPFC at a 2 mA during 30 min. Nicotine cravings, cigarette consumption and decision-making were assessed before and after each session. RESULTS Main findings include a significant decrease in the number of cigarettes smoked when participants received active as compared to sham stimulation. This effect lasted up to four days after the end of the stimulation regimen. In regards to decision-making, smokers rejected more often offers of cigarettes, but not offers of money, after they received active as compared to sham stimulation at the Ultimatum Game. No significant change was observed at the Risk Task with cigarettes or money as rewards. CONCLUSION Overall, these findings suggest that tDCS over the DLPFC may be beneficial for smoking reduction and induce reward sensitive effects.

The autobiographical IAT: a review

The autobiographical Implicit Association Test (aIAT; Sartori et al., 2008) is a variant of the Implicit Association Test (IAT; Greenwald et al., 1998) that is used to establish whether an autobiographical memory is encoded in the respondents mind/brain. More specifically, with the aIAT, it is possible to evaluate which one of two autobiographical events is true. The method consists of a computerized categorization task. The aIAT includes stimuli belonging to four categories, two of them are logical categories and are represented by sentences that are always true (e.g., I am in front of a computer) or always false (e.g., I am climbing a mountain) for the respondent; two other categories are represented by alternative versions of an autobiographical event (e.g., I went to Paris for Christmas, or I went to New York for Christmas), only one of which is true. The true autobiographical event is identified because, in a combined block, it gives rise to faster reaction times when it shares the same motor response with true sentences. Here, we reviewed all the validation experiments and found more than 90% accuracy in detecting the true memory. We show that agreement in identifying the true autobiographical memory of the same aIAT repeated twice is, on average, more than 90%, and we report a technique for estimating accuracy associated with a single classification based on the D-IAT value, which may be used in single subjects investigations. We show that the aIAT might be used to identify also true intentions and reasons and conclude with a series of guidelines for building an effective aIAT.

Brain stimulation over Broca's area differentially modulates naming skills in neurotypical adults and individuals with Asperger's syndrome.

In the present study we tested the hypothesis that, in subjects with Asperger’s syndrome (ASP), the dynamics of language‐related regions might be abnormal, so that repetitive transcranial magnetic stimulation (rTMS) over Broca’s area leads to differential behavioral effects as seen in neurotypical controls. We conducted a five‐stimulation‐site, double‐blind, multiple crossover, pseudo‐randomized, sham‐controlled study in 10 individuals with ASP and 10 age‐ and gender‐matched healthy subjects. Object naming was assessed before and after low‐frequency rTMS of the left pars opercularis, left pars triangularis, right pars opercularis and right pars triangularis, and sham stimulation, as guided stereotaxically by each individual’s brain magnetic resonance imaging. In ASP participants, naming improved after rTMS of the left pars triangularis as compared with sham stimulation, whereas rTMS of the adjacent left opercularis lengthened naming latency. In healthy subjects, stimulation of parts of Broca’s area did not lead to significant changes in naming skills, consistent with published data. Overall, these findings support our hypothesis of abnormal language neural network dynamics in individuals with ASP. From a methodological point of view, this work illustrates the use of rTMS to study the dynamics of brain–behavior relations by revealing the differential behavioral impact of non‐invasive brain stimulation in a neuropsychiatric disorder.

The detection and the neural correlates of behavioral (prior) intentions

Prior intentions are abstract mental representations that are believed to be the prime cause of our intentional actions. To date, only a few studies have focused on the possibility that single prior intentions could be identified in peoples minds. Here, for the first time, we used the autobiographical Implicit Association Test (aIAT) in order to identify a specific prior intention on the basis of a pattern of associations derived from reaction times (Experiment 1). The aIAT is based on two critical blocks: the block associating intentions with true sentences (congruent block) gave rise to faster reaction times (RTs) than the block associating intentions with false sentences (incongruent block). Furthermore, when comparing intentions with hopes, it was revealed that the reported effect was intention-specific: The pattern of associations reflected a congruency effect when intentions and the logical category “True” were paired, but not when hopes and the “True” category were paired (Experiment 2). Finally, we investigated the neural bases of the congruency effect that leads to the identification of an intention (Experiment 3). We found a reduced late positive component (LPC) for the incongruent with respect to the congruent block, suggesting that the incongruent block needs additional resources of cognitive control with respect to the congruent block.

Detrimental effects of using negative sentences in the autobiographical IAT

The autobiographical Implicit Association Test (aIAT) is a method that accurately identifies which one of two contrasting autobiographical events is true for the subject. The aIAT indexes the real autobiographical event (e.g. I was in Paris for Christmas) on the basis of the facilitating effect because it maps the real autobiographical event with true sentences (e.g. I am in front of a computer) on the same motor response. In this paper we focus on the conditions under which the autobiographical IAT accurately and reliably identifies autobiographical memories. A recent study showed a reduction in the accuracy of the aIAT when negative sentences are used. We have investigated the detrimental effect on aIAT accuracy of such negative sentence items, used to describe autobiographical events, compared with affirmative sentence items. While we highlight the reliability of the results obtained using negative sentences, we also show that the use of affirmative sentences in describing autobiographical events guarantees high accuracy and reliability of results in identifying the true autobiographical event. Finally, we summarise the criteria for preparing stimuli for an effective aIAT in order to maximise correct classifications of individual subjects.

True and False DRM Memories: Differences Detected with an Implicit Task.

Memory is prone to illusions. When people are presented with lists of words associated with a non-presented critical lure, they produce a high level of false recognitions (false memories) for non-presented related stimuli indistinguishable, at the explicit level, from presented words (DRM paradigm). We assessed whether true and false DRM memories can be distinguished at the implicit level by using the autobiographical IAT (aIAT), a novel method based on indirect measures that permits to detect true autobiographical events encoded in the respondent’s mind/brain. In our experiment, after a DRM task participants performed two aIATs: the first aimed at testing implicit memory for presented words (true-memories aIAT) and the second aimed at evaluating implicit memory for critical lures (false-memories aIAT). Specifically, the two aIATs assessed the association of presented words and critical lures with the logical dimension “true.” Results showed that the aIAT detected a greater association of presented words than critical lures with the logical dimension “true.” This result indicates that although true and false DRM memories are indistinguishable at the explicit level a different association of the true and false DRM memories with the logical dimension “true” can be detected at the implicit level, and suggests that the aIAT may be a sensitive instrument to detect differences between true and false DRM memories.

Report of a delayed seizure after low frequency repetitive Transcranial Magnetic Stimulation in a chronic stroke patient

We report a seizure in a stroke patient 24 h after exposure to 1 Hz repetitive Transcranial Magnetic Stimulation (rTMS). This 56-year-old man (initials: BS) had suffered a right parietal stroke 8 months prior. MRI scan showed an ischemic lesion in the region of the right middle cerebral artery mainly involving the parieto-temporal areas. The neuropsychological evaluation three months after the stroke showed evidence of visual hemispatial neglect and extinction and he was enrolled in a research study where rTMS was used to relieve the symptoms of visual extinction. He met all inclusion criteria, had no risk factor for TMS, was not taking antiepileptic or epileptogenic drugs, and had never had a seizure. At the time of the enrolment in the study he was suffering from essential hypertension for which he was taking nebivolol and irbesartan; he was also treated with statins and acetylsalicylic acid. The study was three weeks long. During the first week we completed baseline behavioral testing, which consisted of computerized tasks and a complete neuropsychological evaluation that confirmed the presence of visual extinction deficits. In addition, we determined resting motor threshold (RMT) to set the intensity of TMS for the subsequent intervention sessions. RMT was defined as the minimum TMS intensity necessary to elicit a motor response on 5 out of 10 consecutive trials. Stimulation was performed using a 70 mm figure-8-coil connected to a Magstim Rapid (Magstim Co., UK), and his RMT was 74% of machine output intensity. During the second week he underwent 5 days of sham stimulation sessions followed, during the third week, by 5 days of daily active stimulation sessions. Stimulation was applied as 1-Hz rTMS and 90% RMT intensity over the intact left parietal cortex for 20 min (with the coil centered over the electrode location P3 identified using the 10/20 EEG measurement system). For the active stimulation condition, the coil was held with the handle pointing toward the back of the head and positioned perpendicularly to the stimulated region, while for the sham stimulation the coil was tilted at 90 deg, oriented perpendicular to the scalp, with the border of one wing placed against the subject’s scalp. On day 5 of each week he was re-tested on the computerized tests as well as on the neuropsychological tests battery. Moreover, he was screened for possible side effects and asked if he had headache, neck pain, scalp pain, hearing difficulties, trouble concentrating or mood changes. He reported none. On Saturday, 24 h after he completed the third week of the experimental protocol, thus following the week of active rTMS sessions, he experienced tonic and then clonic movements of the left part of the body lasting about 4–5 min. There were no preceding symptoms, no nausea and no postictal confusion; he only reported to be exhausted. He was rapidly assisted by the doctor in charge and laid down. The episode ended spontaneously. There was no loss or alteration of consciousness. Postictally, detailed physical examination did not reveal any neurological or cardiovascular abnormal findings or symptoms. BS was started on the antiepileptic drug (levetiracetam) the same day. This was a non-standard clinical decision of the neurologist on call. Four days after the seizure he underwent electroencephalographic recording (EEG) that showed moderate voltage relative focal theta and delta slowing in the right hemisphere, with some low voltage sharply contoured waveforms consistent with probable spike waves noted maximally in the right posterior quadrant and centro-parietal regions. These EEG findings are consistent with likely focal dysfunction in those regions with underlying cortical irritability. To our knowledge this is the first report of a delayed seizure (24 h from the end of the treatment) following consecutive rTMS therapeutic sessions in a chronic stroke patient. Delayed seizures following single pulse TMS three and four weeks after stimulation were described by Kandler (1990) in two multiple sclerosis (MS) patients over a total of 108 patients. Given the prevalence of epileptic seizures in MS patients (1.1–4.5%) these cases were considered in the normal range. Figiel et al. (1998) also reported a major depression patient who developed a left motor seizure 6 h after 10 Hz rTMS stimulation. In this case the use of antidepressant might have increased the risk of seizures. In addition, one case has been reported of a subject suffering from chronic tinnitus who developed a seizure after one 580-pulses session of 1 Hz rTMS (Nowak et al., 2006), however the seizure in this latter case developed immediately after stimulation. Our patient experienced a focal, simple seizure, arising from the damaged right hemisphere, following a course of 1 Hz rTMS to the left, undamaged hemisphere. Following the stroke, our patient had an increased risk of seizures arising from the right hemisphere. The course of rTMS might have contributed to the seizure by suppressing activity in the intact hemisphere and interhemispherically promoting an increase in excitability in the damaged, right hemisphere (Agosta et al., 2014; Oliveri et al., 1999). Since the time interval between the end of the stimulation session and the seizure was about 24 h, we cannot completely rule out other causes for the ictal episode. It is however unlikely because, according to his medical record and from the patient’s report and he never had seizures before the study. In conclusion, we believe precautions should be taken even when unilateral stroke patients are enrolled in studies where low frequency stimulation is delivered over the undamaged hemisphere. We recommend that patients undergoing multiple rTMS sessions should be monitored up to 24 h after the end of the clinical/experimental trial. It is also worth to point out that notwithstanding the present report, the risk of low-frequency rTMS-induced seizures remains very low at the current state of knowledge.

I didn't want to do it! The detection of past intentions.

In daily life and in courtrooms, people regularly analyze the minds of others to understand intentions. Specifically, the detection of intentions behind prior events is one of the main issues dealt with in courtrooms. To our knowledge, there are no experimental works focused on the use of memory detection techniques to detect past intentions. This study aims at investigating whether reaction times (RTs) could be used for this purpose, by evaluating the accuracy of the autobiographical Implicit Association Test (aIAT) in the detection of past intentions. Sixty healthy volunteers took part in the experiment (mean age: 36.5 y; range: 18–55; 30 males). Participants were asked to recall and report information about a meeting with a person that had occurred at least 1 month before. Half of the participants were required to report about an intentional meeting, whereas the other half reported on a chance meeting. Based on the conveyed information, participants performed a tailored aIAT in which they had to categorize real reported information contrasted with counterfeit information. Results demonstrated that RTs can be a useful measure for the detection of past intentions and that aIAT can detect real past intentions with an accuracy of 95%.

The Pivotal Role of the Right Parietal Lobe in Temporal Attention.

The visual system is extremely efficient at detecting events across time even at very fast presentation rates; however, discriminating the identity of those events is much slower and requires attention over time, a mechanism with a much coarser resolution [Cavanagh, P., Battelli, L., & Holcombe, A. O. Dynamic attention. In A. C. Nobre & S. Kastner (Eds.), The Oxford handbook of attention (pp. 652–675). Oxford: Oxford University Press, 2013]. Patients affected by right parietal lesion, including the TPJ, are severely impaired in discriminating events across time in both visual fields [Battelli, L., Cavanagh, P., & Thornton, I. M. Perception of biological motion in parietal patients. Neuropsychologia, 41, 1808–1816, 2003]. One way to test this ability is to use a simultaneity judgment task, whereby participants are asked to indicate whether two events occurred simultaneously or not. We psychophysically varied the frequency rate of four flickering disks, and on most of the trials, one disk (either in the left or right visual field) was flickering out-of-phase relative to the others. We asked participants to report whether two left-or-right-presented disks were simultaneous or not. We tested a total of 23 right and left parietal lesion patients in Experiment 1, and only right parietal patients showed impairment in both visual fields while their low-level visual functions were normal. Importantly, to causally link the right TPJ to the relative timing processing, we ran a TMS experiment on healthy participants. Participants underwent three stimulation sessions and performed the same simultaneity judgment task before and after 20 min of low-frequency inhibitory TMS over right TPJ, left TPJ, or early visual area as a control. rTMS over the right TPJ caused a bilateral impairment in the simultaneity judgment task, whereas rTMS over left TPJ or over early visual area did not affect performance. Altogether, our results directly link the right TPJ to the processing of relative time.