Streese & Tranel

Combined Lesion-Deficit and fMRI Approaches in Single-Case Studies

Authors and Affiliations

  • Carolina Deifelt Streese 1

  • Daniel Tranel 1,2

    1. Department of Neurology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.

    2. Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, USA.

Correspondence

  • Email:

    • Carolina Deifelt Streese: carolina-deifeltstreese@uiowa.edu

    • Daniel Tranel: daniel-tranel@uiowa.edu

Abstract

  • Despite the foundational role of lesion-deficit case studies, there has been a decline in their publication.

  • This review argues for the unique value of combining single-case lesion-deficit research with functional neuroimaging methods, particularly functional magnetic resonance imaging (fMRI).

  • Summarizes findings from combined lesion-deficit and fMRI studies from 2017 to 2020, demonstrating unique contributions to understanding complex brain functions, connectivity, and recovery.

  • Encouragement for researchers to employ this combined method in analyzing brain-behavior relationships.

Introduction

  • Foundational Role of Lesion-Deficit Studies in Cognitive Neuroscience:

    • Examples of influential cases:

    • Mr. Leborgne: Key in understanding language.

    • S.M.: Insight into emotional processing.

    • Phineas Gage: Connection between personality and brain lesions.

    • Patient H.M.: Discovered hippocampus's role in episodic memory.

  • Nature of Lesion-Deficit Studies:

    • Serendipitous: Lack of control over lesion occurrence provides unique behavioral insights.

    • The unpredictable behaviors prompt new theories and insights into brain-behavior relationships.

    • Case Studies Examples:

    • Loss of ability to name verbs but not nouns indicating dissociation between lexical processes.

  • Decline in Publishing Single-Case Studies:

    • Increased reliance on neuroimaging techniques attributed to the decline.

    • Journals favoring significant or unusual single-case reports.

Combined Lesion-Deficit and fMRI Approach

  • Benefits of Utilizing fMRI with Lesion-Deficit Studies:

    • Enhanced understanding of neural processes and connectivity.

    • Insights into recovery post-brain injury and effects of rehabilitation therapies.

    • Visual processing pathways investigated through case studies highlighting functional brain structures.

Connectivity Insights

  • Functional Imaging and Connectivity:

    • Patterns of brain connectivity assessed through fMRI.

    • Unique lesions offer comparisons to matched control groups, elucidating role of certain brain regions in networks.

  • Findings on Visual Processing:

    • Traditional conceptualization flows from retina to thalamus to visual cortex.

    • New findings show preserved motion perception despite occipital lobe damage in some patients.

    • Cases where patients perceive motion but lack static vision led to discoveries of alternative visual processing pathways.

  • Face Processing Insights:

    • Case of a patient with prosopagnosia suggests non-linear processing of facial information, activating anterior face-processing networks despite damage to posterior regions.

  • Language Networks:

    • Combined analysis elucidated the role of frontal fiber pathways connecting planning and lexical processing regions.

    • Case study found peculiarities in bilingual aphasia with observed disconnections affecting language control networks during fMRI.

Plasticity and Recovery Insights

  • Plasticity Investigations:

    • Examining brain reorganization post-injury through longitudinal fMRI studies of single cases.

    • Case of amnesia linked thalamic damage to previously existing hippocampal lesions; suggests reliance on alternative memory circuits.

    • Example of rapid reorganization in motor cortex under pressure showing adaptation strategies.

  • Request for More Case Studies:

    • Emphasis on the importance of single-case fMRI studies in neuroimaging, offering nuanced insights not captured in group studies.

    • Understanding unique individual recovery trajectories may inform wider rehabilitation practices.

Methodological Limitations

  • Limitations in single-case studies concerning the lack of control over confounding variables affecting neuroimaging outcomes.

  • Importance of including robust matched controls for comparative analysis.

  • Suggestions for employing specific statistical methods tailored to single-case comparisons.

Conclusion

  • The combination of lesion-deficit and fMRI studies enhances understanding of brain organization and plasticity, providing insights into recovery processes.

  • Advocates for the integration of fMRI measures in single-case studies to enrich data collection and improve scientific discovery.

  • A call for journals to reconsider the publication approach for multifaceted single-case studies as academically valuable.

Acknowledgements

  • Research supported by:

    • National Institute of Mental Health (MH094258)

    • National Institutes of Health (NS103780)

    • Kiwanis Neuroscience Research Foundation.

References

  • A comprehensive list of foundational and recent studies supporting the concepts discussed in this review.