A distributed effects perspective of dimensionally defined psychiatric disorders: and convergent versus core deficit effects in ADHD

Abstract

The focus of psychiatric and psychological research has arguably shifted from brain damage and psychosis to more common forms of psychopathology that reflect extremes variants of otherwise normal cognitive and behavioral characteristics. Now, in addition to trying to understand overtly damaged brain-function (flat tire effects), we are also seeking to understand liabilities associated with non-optimized, but otherwise intact, cognitive and behavioral abilities (poor tuning effects). This shift has pushed us to evolve our investigational strategies to more broadly consider whole-brain integrated brain systems, as well as seek to develop more specific quantifiable indicators of impoverished brain function and behavior. This paper discusses such challenges in relation to dimensionally defined psychiatric disorders and presents a novel whole-brain integrated perspective of ADHD brain function pathology.

Keywords: ADHD; attention; brain-state; hemispheres; laterality; model; network; theory.

Figure 1

Possible levels of impairment underlying psychiatric disorders. Legend: multiple levels of brain function levels that might underlie brain function pathology in psychiatric disorders. Lower section (in green) highlights levels more likely to involve automatic processing (i.e., that do not require self-directed effort). Upper section (in blue) highlights levels more likely to require active volitional effort. FPN, fronto-parietal network; DAN, dorsal attention network; VAN, ventral attention network; DMN, default mode network; LD, learning disability.

Figure 2

ADHD comorbidity and primary deficit source considerations. This shows how ADHD comorbidity profiles might help elucidate levels of brain function pathology underlying ADHD. Note: regardless of causal deficit sources, all ADHD producing etiological paths involve impairment at the adaptive state setting level. EF, executive function; LD, learning disorder; Comp., compensated.

Figure 3

Task-directed-adaptive processing state brain system. Legend: shows four primary TD-APS brain system computational nodes. Outer rings represent levels of brain function that could impact TD-APS brain system. Arrows crossing outer rings represent hypothetical unique impairment trajectories with causal deficits originating at different levels of brain function. Purple arrows represent TD-APS intrinsic regulation of automatic sensory responsivity.