This explanation may be supported by Bonner-Jackson and colleagues (2013), who suggest that processing speed is mediated by cognitive reserve in prHD so that individuals with greater prodromal intellect may show less bradyphrenia than similarly burdened prodromal participants with lower premorbid IQ. This rerouting to alternate areas of the brain results in accurate but slowed processing during prHD. Paulsen and colleagues (2011) attribute this phenomenon to the concept of вЂњeffortful processing.вЂќ Effortful processing is the notion that the brain is capable of compensating for dysfunctional circuitry for a given period of time, specifically during the HD prodrome, by recruiting surrogate regions of the brain to complete cognitive tasks. Despite common deficits in processing speed, persons who have this symptom in prHD do not typically have highly correlated decline in functioning ( Duff et al., 2010a). Third, other subtle components of HD, such as perceptual processing ( O'Rourke et al., 2011) and oculomotor scanning ( Blekher et al., 2004, 2006), are impacted in prHD and could weaken processing speed ( Paulsen, 2011). Next, it is clear that processing speed can be slowed in the presence of psychiatric symptoms, such as depression ( Smith et al., 2012), and many participants with prHD have psychiatric symptoms. For example, the Digit Symbol subtest of the Wechsler Adult Intelligence Scales has shown that impairments were present in numerous acquired, developmental, and degenerative brain conditions. First, it has long been known that cognitive processing speed is one of the most sensitive (though nonspecific) cognitive abilities demonstrating decline with cerebral dysfunction ( Lezak, 2012).

There are likely several reasons for the sensitivity of timed tasks on cognitive performance. Across all three prHD subgroups (prHDI, prHDII, and prHDIII), as well as postdiagnosis stages of HD (IвЂ“III), processing speed exhibits a linear trend in decline. Processing speed is thought to be the most common cognitive deficit affecting individuals with prHD ( Maroof et al., 2011 Paulsen, 2011). Emily Shaw, in Handbook of Clinical Neurology, 2017 Processing speed Neurocognitive testing often includes evaluation of speed by assessing response time in both verbal and motor modalities. Neuropathologically, this process is driven by the speed of neuronal transmissions, is associated with myelination ( Chopra etВ al., 2018), and damage to the subcortical white matter often gives rise to processing speed deficits ( Turken etВ al., 2008). However, processing speed can be dissociated from other cognitive domains and subdomains ( Agelink van Rentergem etВ al., 2020). Deficient processing speed can limit cognitive processing in other cognitive domains (e.g., placing a limit on the amount of information that can be attended to or encoded at one time). Processing speed is sometimes considered a core constituent of attention indeed, most tests of attention are speed-sensitive if not speed-dependent, although some specialized neurocognitive tests separate attentional accuracy from speed of responsiveness. Processing speed refers to (as the name implies) the speed with which information can be sensed, perceived, understood, and responded to. Lee, in Reference Module in Neuroscience and Biobehavioral Psychology, 2021 Processing speed

Average speed symbol