Abstract
Drawing on theoretical and computational work with the localist dual route reading model and results from behavioral studies, Besner et al. (2011) proposed that the ability to perform tasks that require overriding stimulus-specific defaults (e.g., semantics when naming Arabic numerals, and phonology when evaluating the parity of number words) necessitate the ability to modulate the strength of connections between cognitive modules for lexical representation, semantics, and phonology on a task- and stimulus-specific basis. We used functional magnetic resonance imaging to evaluate this account by assessing changes in functional connectivity while participants performed tasks that did and did not require such stimulus-task default overrides. The occipital region showing the greatest modulation of BOLD signal strength for the two stimulus types was used as the seed region for Granger causality mapping (GCM). Our GCM analysis revealed a region of rostromedial frontal cortex with a crossover interaction. When participants performed tasks that required overriding stimulus type defaults (i.e., parity judgments of number words and naming Arabic numerals) functional connectivity between the occipital region and rostromedial frontal cortex was present. Statistically significant functional connectivity was absent when the tasks were the default for the stimulus type (i.e., parity judgments of Arabic numerals and reading number words). This frontal region (BA 10) has previously been shown to be involved in goal-directed behavior and maintenance of a specific task set. We conclude that overriding stimulus-task defaults requires a modulation of connection strengths between cognitive modules and that the override mechanism predicted from cognitive theory is instantiated by frontal modulation of neural activity of brain regions specialized for sensory processing.
Highlights
The chain from sensation to perception and action is forged by context, and experience predisposes us to interpret certain stimuli in particular ways
response times (RTs) for the naming/reading-aloud task were faster than RTs for the parity task, F(1,12) = 73.2, MSE = 4669.5, p < 0.001
Because functional roles have been established for many brain regions, the specific brain region indicated by an fMRI study and its functional associations can be used to evaluate the plausibility of a particular cognitive account
Summary
The chain from sensation to perception and action is forged by context, and experience predisposes us to interpret certain stimuli in particular ways. Besner et al (2011) found that participants were much faster at making parity judgments to Arabic numerals than to numbers presented alphabetically (hereafter referred to as “number words”), but took about the same amount of time when reading/naming these different stimuli aloud. Besner et al (2011) found that participants were much faster at making parity judgments to Arabic numerals than to numbers presented alphabetically (hereafter referred to as “number words”), but took about the same amount of time when reading/naming these different stimuli aloud1 To explain their findings, Besner et al (2011) proposed a general account in which there are various special purpose modules, each of which computes specific information-processing routines. The additional but theoretically central point here is that the strength of the format-task associations reflects both predispositions (some format-task pairings are more natural and experienced than others; Figure 1A), and task-induced modulation of the routes connecting the relevant cognitive modules (Figure 1B)
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