Periodic Reporting for period 1 - NEUROINTELLIGENCE (The Brain Dynamics of Human Fluid Intelligence)
Berichtszeitraum: 2018-04-01 bis 2020-03-31
Human fluid intelligence (FI) is characterized by a structured sequence of cognition, resulting in efficient application of rules to novel problems. In the brain, metabolic neuroimaging and lesion studies have linked FI to a specific frontoparietal network, here called the multiple-demand (MD) network, comprising regions of lateral frontal, insular, dorsomedial frontal and parietal cortex. But how do MD functions determine FI across stages of cognition? My extensive expertise in electroencephalography (EEG) source analyses allowed me to assess time-resolved neural representations of novel rules in MD and perceptual cortex as a function of FI, as well as the causal impact of MD cortex on earliest stages of perceptual encoding and task-related retrieval of information from memory. Higher- and lower-intelligent subjects’ EEG and behavioral measures of novel rule implementation have been systematically analyzed. Non-invasive neural stimulation (transcranial magnetic stimulation (TMS)) was used in combination with EEG to draw causal conclusions on the specific role of MD cortices in human FI. This novel analysis approach has provided a new account on FI: one aspect of low FI is the dysfunctional early filtering and retrieval of task-relevant information from memory, due to lack of top-down control from MD cortices, leading to cognitive overload on later processing stages.
The results of the two studies suggest that indeed higher intelligent subjects not only showed better task performance, but also stronger neural responses in an early time window of task processing in the right intraparietal cortex, a region known to be involved in semantic fact retrieval. TMS stimulation of this region improved performance of both higher and lower intelligent subjects, while specifically the lower intelligent subjects showed a boost in right intraparietal neural activation patterns in response to the TMS triple-pulse. This suggests that specific TMS-based interventions that aim to address the cognitive functions underlying FI may be especially beneficial for those who show deficits in this cognitive domain.
The proposal’s outcomes are both of high academic and clinical interest. Understanding the brain signatures underlying FI is essential for more specific and cost-effective medical interventions. For example, decline of FI due to specific diseases or healthy ageing is strongly correlated with psychiatric conditions such as depression, which affect an increasing number of people in the ageing European population. Developing more targeted neuroscientific interventions in this area will reduce the duration and cost of other medical interventions, such as the treatment with psychopharmaca and psychotherapy.
The results of the two studies suggest that indeed higher intelligent subjects not only showed better task performance, but also stronger neural responses in an early time window of task processing in the right intraparietal cortex, a region known to be involved in semantic fact retrieval. TMS stimulation of this region improved performance of both higher and lower intelligent subjects, while specifically the lower intelligent subjects showed a boost in right intraparietal neural activation patterns in response to the TMS triple-pulse. This suggests that specific TMS-based interventions that aim to address the cognitive functions underlying FI may be especially beneficial for those who show deficits in this cognitive domain.
The proposal’s outcomes are both of high academic and clinical interest. Understanding the brain signatures underlying FI is essential for more specific and cost-effective medical interventions. For example, decline of FI due to specific diseases or healthy ageing is strongly correlated with psychiatric conditions such as depression, which affect an increasing number of people in the ageing European population. Developing more targeted neuroscientific interventions in this area will reduce the duration and cost of other medical interventions, such as the treatment with psychopharmaca and psychotherapy.
The proposal included two neuroscientific projects, an EEG study as well as a combined EEG-TMS study. Those have been both completed, i.e. data of 40 volunteers were collected for each project, respectively, and the data have been analysed.
I used EEG and combined EEG-TMS to assess the specific role of the frontoparietal MD system in human FI. Specifically, I asked whether low FI may be due to the dysfunctional early memory retrieval of task-relevant information. Data from the first EEG project indeed suggest that first neural differences between higher and lower intelligent subjects specifically occur at early neural processing stages within the MD system: around 200 milliseconds post task-onset, right intraparietal cortex showed stronger neural responses for higher intelligent subjects (Figure 1A). This effect was specific, i.e. it neither occurred in other brain regions nor at a different point in time. Stronger neural signatures of higher intelligent subjects were accompanied by their significantly better task performance (Figure 1B), and lower numbers of missed targets significantly correlated with stronger neural responses in right intraparietal cortex (Figure 1C). The right intraparietal cortex has been frequently associated with processes of semantic memory retrieval, suggesting that better task performance measures in higher intelligent subjects were due to more efficient early memory retrieval of task-relevant information.
In the second project, the combined EEG-TMS study, TMS was used to stimulate right intraparietal cortex in the time interval in which neural differences between higher and lower intelligent subjects were observed in the first project, i.e. in the EEG study. The same task paradigm was used as in the first project. TMS stimulation evoked a strong neural response in that region. Interestingly, a stronger TMS induced boost in neural responses was specifically observed in the group of lower intelligent subjects in right parietal cortex (Figure 2A), suggesting that TMS had a stronger impact on this group, compared with higher intelligent subjects, who already showed relatively strong neural responses in right parietal cortex in no-TMS conditions (i.e. in the first EEG project). Higher intelligent subjects showed significantly better task performance across all conditions (i.e. with and without TMS stimulation) relative to lower intelligent subjects (Figure 2B), thus replicating results from the first EEG project. Strikingly, the right intraparietal TMS stimulation caused a significant improvement in task performance in both higher and lower intelligent subjects (Figure 2C). Considering the specific boot of neural responses in lower intelligent subjects, this novel evidence may suggest that right parietal TMS stimulation has an especially beneficial impact on the cognitive processes of lower intelligent subjects. Follow-up research will tell whether this applies as well to populations suffering from a decline in FI due to illness or natural ageing.
The current results have been presented on multiple conferences, namely the SAMBA conference in Salzburg 2018 and the OHBM conference in Rom 2019. Preliminary results have been also presented to the EU at the MSCA-IF monitoring at LMU in May 2019, and received a very positive feedback. Furthermore, a talk on the projects’ outcomes has been accepted for a symposium at the BIOMAG-2020 conference in August 2020 in Birmingham. A manuscript has been prepared for submission to a high-impact peer-reviewed journal, such as PLOS Biology or PNAS.
I used EEG and combined EEG-TMS to assess the specific role of the frontoparietal MD system in human FI. Specifically, I asked whether low FI may be due to the dysfunctional early memory retrieval of task-relevant information. Data from the first EEG project indeed suggest that first neural differences between higher and lower intelligent subjects specifically occur at early neural processing stages within the MD system: around 200 milliseconds post task-onset, right intraparietal cortex showed stronger neural responses for higher intelligent subjects (Figure 1A). This effect was specific, i.e. it neither occurred in other brain regions nor at a different point in time. Stronger neural signatures of higher intelligent subjects were accompanied by their significantly better task performance (Figure 1B), and lower numbers of missed targets significantly correlated with stronger neural responses in right intraparietal cortex (Figure 1C). The right intraparietal cortex has been frequently associated with processes of semantic memory retrieval, suggesting that better task performance measures in higher intelligent subjects were due to more efficient early memory retrieval of task-relevant information.
In the second project, the combined EEG-TMS study, TMS was used to stimulate right intraparietal cortex in the time interval in which neural differences between higher and lower intelligent subjects were observed in the first project, i.e. in the EEG study. The same task paradigm was used as in the first project. TMS stimulation evoked a strong neural response in that region. Interestingly, a stronger TMS induced boost in neural responses was specifically observed in the group of lower intelligent subjects in right parietal cortex (Figure 2A), suggesting that TMS had a stronger impact on this group, compared with higher intelligent subjects, who already showed relatively strong neural responses in right parietal cortex in no-TMS conditions (i.e. in the first EEG project). Higher intelligent subjects showed significantly better task performance across all conditions (i.e. with and without TMS stimulation) relative to lower intelligent subjects (Figure 2B), thus replicating results from the first EEG project. Strikingly, the right intraparietal TMS stimulation caused a significant improvement in task performance in both higher and lower intelligent subjects (Figure 2C). Considering the specific boot of neural responses in lower intelligent subjects, this novel evidence may suggest that right parietal TMS stimulation has an especially beneficial impact on the cognitive processes of lower intelligent subjects. Follow-up research will tell whether this applies as well to populations suffering from a decline in FI due to illness or natural ageing.
The current results have been presented on multiple conferences, namely the SAMBA conference in Salzburg 2018 and the OHBM conference in Rom 2019. Preliminary results have been also presented to the EU at the MSCA-IF monitoring at LMU in May 2019, and received a very positive feedback. Furthermore, a talk on the projects’ outcomes has been accepted for a symposium at the BIOMAG-2020 conference in August 2020 in Birmingham. A manuscript has been prepared for submission to a high-impact peer-reviewed journal, such as PLOS Biology or PNAS.
This project provides novel evidence on the crucial role of right parietal cortex in FI dependent cognitive processing, as well as on the facilitating effect of triple-pulse TMS stimulation on cognitive functions underlying FI. The fact that, on the neural level, stronger TMS-related boosting was observed in subjects who previously showed weaker neural responses and lower task performance, may suggest a specifically positive impact of TMS-interventions in those groups of the general population who suffer from aspects of - age or illness related – (temporal) decline of FI. Thus, the findings of this Marie Curie project pave the way towards more targeted neuroscientific clinical interventions. These are of great importance for the treatment of specific psychiatric conditions causing temporal deficits in FI, such as schizophrenia and depression, as well as for the treatment of an increasing number of patients suffering from age-related cognitive decline in the ageing European population.