Hemispheric activation differences in novice and expert clinicians during clinical decision making

Abstract

Clinical decision making requires knowledge, experience and analytical/non-analytical types of decision processes. As clinicians progress from novice to expert, research indicates decision-making becomes less reliant on foundational biomedical knowledge and more on previous experience. In this study, we investigated how knowledge and experience were reflected in terms of differences in neural areas of activation. Novice and expert clinicians diagnosed simple or complex (easy, hard) cases while functional magnetic resonance imaging (fMRI) data were collected. Our results highlight key differences in the neural areas activated in novices and experts during the clinical decision-making process. fMRI data were collected from ten second year medical students (novices) and ten practicing gastroenterologists (experts) while they diagnosed sixteen (eight easy and eight hard) clinical cases via multiple-choice questions. Behavioral data were collected for diagnostic accuracy (correct/incorrect diagnosis) and time taken to assign a clinical diagnosis. Two analyses were performed with the fMRI data. First, data from easy and hard cases were compared within respective groups (easy > hard, hard > easy). Second, neural differences between novices and experts (novice > expert, expert > novice) were assessed. Experts correctly diagnosed more cases than novices and made their diagnoses faster than novices on both easy and hard cases (all p’s < 0.05). Time taken to diagnose hard cases took significantly longer for both novices and experts. While similar neural areas were activated in both novices and experts during the decision making process, we identified significant hemispheric activation differences between novice and expert clinicians when diagnosing hard clinical cases. Specifically, novice clinicians had greater activations in the left anterior temporal cortex and left ventral lateral prefrontal cortex whereas expert clinicians had greater activations in the right dorsal lateral, right ventral lateral, and right parietal cortex. Hemispheric differences in activation were not observed between novices and experts while diagnosing easy clinical cases. While clinical decision-making engaged the prefrontal cortex (PFC) in both novices and experts, interestingly we observed expertise related differences in the regions and hemispheres of PFC activation between these groups for hard clinical cases. Specifically, in novices we observed activations in left hemisphere neural regions associated with factual rule-based knowledge, whereas in experts we observed right hemisphere activation in neural regions associated with experiential knowledge. Importantly, at the neural level, our data highlight differences in so called type 2 clinical decision-making processes related to prior knowledge and experience.

Appendix: fMRI basics

Functional magnetic resonance imaging (fMRI) images are made possible by tracking hemodynamic response to neural activity over time (Huettel et al. 2009; Logothetis 2003). When neurons become active in response to a task or demand, hemodynamic changes of increased blood volume, increased blood flow and alterations in oxygenation occur (Attwell and Iadecola 2002; Heeger and Ress 2002). These changes produce the blood oxygen level dependent (BOLD) signal, which can be simplistically described as a ratio of oxygenated to deoxygenated hemoglobin (Ashby 2011). The underlying assumption in fMRI is that increased oxyhemoglobin concentration indicates nearby neural activity (Savoy 2001).

A block design was chosen for this research, where tasks were presented in a sequential manner with alternating periods of stimulation and rest (Amaro and Barker 2006). Specifically, experimental blocks of clinical decision-making tasks (multiple choice questions), alternated with rest blocks called fixation periods. Fixation periods served as baseline, and can be thought of as a control condition during which no task is being performed (Raichle and Mintun 2006). In fixation periods, no text was presented and no response was expected from participants; it involved simply looking at a plus sign (fixation cross) on the screen for 10 s intervals.

To determine neural areas of activation in clinical decision making, averaged neural activity across fixation trials were contrasted to averaged neural activity in defined clinical decision making experimental blocks (answering MCQ). When differences in level of activation were found to be greater during the experimental phase of the task (i.e. during decision making) than activation during fixation (baseline/rest), neural activity is interpreted as being attributed to the cognitive process of clinical decision making (Amaro and Barker 2006).

Subject data obtained in this fMRI research are representative of each participant’s brain. These pieces of data are called voxels, analogous to 3D pixels, and are volumetric in nature (Ashby 2011). Each voxel is represented by 3D coordinates (x, y, z), which are used to identify associated structural areas using brain atlas tools.