Transferring Cognitive Tasks Between Brain Imaging Modalities: Implications for Task Design and Results Interpretation in fMRI Studies

Summary

Transferring a paradigm with a history of use in EEG experiments to an fMRI experiment is considered. It is demonstrated that manipulating the task demands in the visual oddball task resulted in different patterns of BOLD activation and illustrated how task design is crucial in fMRI experiments.

Abstract

As cognitive neuroscience methods develop, established experimental tasks are used with emerging brain imaging modalities. Here transferring a paradigm (the visual oddball task) with a long history of behavioral and electroencephalography (EEG) experiments to a functional magnetic resonance imaging (fMRI) experiment is considered. The aims of this paper are to briefly describe fMRI and when its use is appropriate in cognitive neuroscience; illustrate how task design can influence the results of an fMRI experiment, particularly when that task is borrowed from another imaging modality; explain the practical aspects of performing an fMRI experiment. It is demonstrated that manipulating the task demands in the visual oddball task results in different patterns of blood oxygen level dependent (BOLD) activation. The nature of the fMRI BOLD measure means that many brain regions are found to be active in a particular task. Determining the functions of these areas of activation is very much dependent on task design and analysis. The complex nature of many fMRI tasks means that the details of the task and its requirements need careful consideration when interpreting data. The data show that this is particularly important in those tasks relying on a motor response as well as cognitive elements and that covert and overt responses should be considered where possible. Furthermore, the data show that transferring an EEG paradigm to an fMRI experiment needs careful consideration and it cannot be assumed that the same paradigm will work equally well across imaging modalities. It is therefore recommended that the design of an fMRI study is pilot tested behaviorally to establish the effects of interest and then pilot tested in the fMRI environment to ensure appropriate design, implementation and analysis for the effects of interest.

Introduction

As cognitive neuroscience methods develop, established experimental tasks are used with emerging brain imaging modalities. This is a logical progression since most neuropsychological concepts (e.g., distinct memory sub-components) have been investigated in the behavioral domain and appropriate experimental tasks for probing specific functions have been developed and tested. As new technology emerges evidence for the neural underpinnings of these behavioral observations is sought with the new brain imaging methods. While it may be tempting to simply draw on well-studied behavioral tasks for imaging studies, several important caveats have to be taken into accou....

Protocol

NOTE: The study protocol was approved by the local Human Subjects Review Board at RWTH Aachen University and was carried out in accordance with the Declaration of Helsinki.

1. Task Design

1. Choose an appropriate task to investigate the cognitive/psychological construct of interest. Use the visual oddball task (Figure 1) to measure target detection responses and the effects of attention on target detection. This allows investigation of the influence of task manipulations on fMRI data.
2. Use three versions of the oddball task.
   1. Passive version: Ask the subject to observe visual stimuli. D....

Results

The stimulation and analysis method elicited BOLD activation in brain regions associated with a visual oddball task. The target > non-target contrast revealed no activation for the passive condition but did reveal activation in both the count and respond (Figure 3). The data presented in Figure 3 is a qualitative comparison of the count and respond conditions and shows how the activation patterns would look if each version of the task was performed in isolation.

Discussion

We show that manipulating the task demands in the visual oddball task results in different patterns of BOLD activation in the count and respond conditions. The functional roles of some of the regions implicated in each condition would have been inappropriately assigned had data from the three versions of the task not been available for comparison. This ambiguity in data interpretation would not necessarily have been the case in the EEG P300 field where the task has its origin, highlighting the need for .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Magnetom Tim Trio 3 T MRI scanner	Siemens Medical Solutions, Erlangen, Germany
Presentation version 14.8	Neurobehavioural system, Albany, CA, USA
Lumitouch device	Photon Control Inc, Burnaby, BC, Canada		This device is no longer produced by the manufacturer. Alternative MR compatible response devices are available.
TFT display	Apple, Cupertino, CA, USA	30 inch cinema display	The screen was custom modified in-house to be MR compatible. However, a number of MR compatible screens are available on the market.
Optseq		surfer.nmr.mgh.harvard.edu/optseq	program for determining optimal stimulus timing for rapid event related designs
FMRIB software library (FSL)	FMRIB, Oxford	http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/	Other software tools are available for analyzing fMRI data, for example SPM, AFNI and Brain Voyager.