Investigating Subcortical Involvement in Working Memory Updating Processes Using Ultra-High Field 7T MRI

Główne pojęcia

Subcortical regions, particularly the basal ganglia and dopaminergic midbrain, play a key role in various working memory updating subprocesses, including gate closing, substitution, and the general updating mode, but not in gate opening.

Streszczenie

This study used ultra-high field 7T fMRI to investigate the subcortical involvement in different working memory updating subprocesses. The key findings are:

1. Gate opening was associated with widespread cortical activation, including frontal, parietal, and occipital regions, as well as the thalamus. However, the ROI analyses provided only weak evidence for thalamic involvement, suggesting inconclusive results for subcortical engagement during gate opening.

2. During gate closing, the ROI analyses indicated moderate evidence for involvement of the right globus pallidus externa (GPe) and weak evidence for the right striatum and subthalamic nucleus (STN), as well as bilateral substantia nigra (SN). This suggests a role for basal ganglia and dopaminergic midbrain regions in the process of closing the working memory gate.

3. Substitution, the process of replacing old information with new in working memory, was associated with activation in the striatum bilaterally, right STN, and right ventral tegmental area (VTA). This indicates engagement of the basal ganglia and dopaminergic midbrain regions in the actual updating of working memory content.

4. Being in an updating mode, independent of whether updating was required, was linked to activity in the left and right globus pallidus externa (GPe), right STN, and right SN. This suggests a more general involvement of basal ganglia and dopaminergic midbrain regions in maintaining an open state of the working memory gate.

Overall, the findings expand our understanding of the subcortical regions involved in working memory updating, providing evidence for the role of the basal ganglia and dopaminergic midbrain, particularly during gate closing, substitution, and the general updating mode, but not during gate opening.

Statystyki

The mean response time (RT) for correct responses was 0.85 seconds, and the overall accuracy on the task was 94.7%.
Responses were slower and less accurate on reference/switch trials compared to reference/repeat trials, indicating a behavioral cost of working memory gate opening.
The difference in RT between "same" and "different" responses was larger for repeated reference trials compared to repeated comparison trials, suggesting a cost of working memory substitution.
Responses were slower but more accurate on repeated reference trials compared to repeated comparison trials, reflecting the response time cost of being in a general updating mode.

Cytaty

"Gate opening was associated with large bilateral clusters of activation across the cortex, including frontal, parietal, and occipital regions, as well as the thalamus."
"Gate closing was associated with a few clusters of cortical activations, including the left posterior parietal cortex and left dorsolateral prefrontal cortex."
"Substitution was associated with increased activation in the premotor cortex, prefrontal cortex, pre-supplementary motor area, parietal cortex, and subcortical regions including the striatum."
"Being in an updating mode was associated with increased activation in frontal, posterior parietal, and occipital regions, as well as the striatum, caudate nuclei, and thalamus."

Kluczowe wnioski z

Investigating working memory updating processes of the human subcortex using 7 Tesla fMRI

by Trutti,A. C.... o www.biorxiv.org 03-14-2024

https://www.biorxiv.org/content/10.1101/2024.03.14.584970v2

Głębsze pytania

What are the potential implications of the differential involvement of basal ganglia and dopaminergic midbrain regions in the various working memory updating subprocesses

The differential involvement of basal ganglia and dopaminergic midbrain regions in the various working memory updating subprocesses has several potential implications. Firstly, the findings suggest that the basal ganglia and midbrain regions play distinct roles in working memory updating. The basal ganglia, particularly the striatum, appear to be more involved in specific subprocesses like substitution, while the midbrain regions, such as the substantia nigra and ventral tegmental area, show differential activation across gate closing, substitution, and updating mode contrasts. This differential involvement implies a complex interplay between these subcortical regions in regulating working memory processes. Understanding these specific roles can provide insights into the underlying neural mechanisms of working memory updating and how different subprocesses are orchestrated by the basal ganglia and dopaminergic midbrain regions.

How might the findings from this study inform our understanding of the role of dopamine in cognitive flexibility and the stability-flexibility trade-off in working memory

The findings from this study can inform our understanding of the role of dopamine in cognitive flexibility and the stability-flexibility trade-off in working memory. Dopamine, a key neuromodulator, is known to influence cognitive functions, including working memory updating. The differential activation of dopaminergic midbrain regions during various working memory subprocesses suggests that dopamine plays a crucial role in regulating cognitive flexibility. Specifically, the involvement of the substantia nigra and ventral tegmental area in updating mode and substitution processes indicates that dopamine signaling is essential for adapting to new information and updating working memory representations. These findings support the idea that dopamine modulates the balance between cognitive stability (maintaining existing information) and flexibility (updating information) in working memory. By elucidating the specific contributions of dopaminergic pathways to working memory updating, this study enhances our understanding of the neural mechanisms underlying cognitive flexibility and the stability-flexibility trade-off in working memory.

Given the focus on subcortical regions, how might the findings from this study relate to the pathophysiology of neurological and psychiatric disorders characterized by working memory deficits, such as Parkinson's disease or schizophrenia

The focus on subcortical regions in this study has implications for understanding the pathophysiology of neurological and psychiatric disorders characterized by working memory deficits, such as Parkinson's disease or schizophrenia. The differential activation of basal ganglia and dopaminergic midbrain regions in working memory subprocesses provides valuable insights into how dysfunction in these areas may contribute to working memory impairments in these disorders. For example, in Parkinson's disease, which is characterized by dopamine depletion and basal ganglia dysfunction, the findings of altered activation patterns in the basal ganglia and midbrain during working memory tasks could help explain the working memory deficits observed in individuals with this condition. Similarly, in schizophrenia, which is associated with dopamine dysregulation and abnormalities in subcortical regions, understanding how these regions are involved in working memory updating subprocesses could shed light on the cognitive symptoms of the disorder. Overall, the findings from this study offer a neurobiological basis for understanding working memory deficits in these disorders and may guide future research on targeted interventions for improving working memory function in clinical populations.