Dyscalculia and vestibular function
Introduction
It was first reported in the early 1990s that people with damage to the balance organs of the inner ear (the ‘vestibular system’), exhibited deficits in memories for places in the environment (i.e., ‘spatial memory’) [see [1] for review]. Given that the vestibular system detects movement of the head in three dimensional space, performs complex mathematical computations of acceleration, velocity and position of the head [2] and communicates this information to higher centres of the brain [3], [4], [5], [6], this was perhaps not entirely surprising. The first clinical evidence was published by Grimm et al. in 1989 [7], who reported that patients with a perilymph fistular syndrome (a rupture in the vestibular labyrinth, resulting in leakage of perilymphatic fluid) experienced not only vestibular symptoms (e.g., positional vertigo) but also a variety of cognitive and emotional symptoms, including memory and attention deficits, anxiety and depression. From a total sample of 102 patients, more than 85% reported memory loss of some sort. Despite a normal level of intellectual function, performance on digit symbol, block design, paired associate learning and picture arrangement tasks, was impaired.
Since this study, many papers have been published documenting specific spatial memory and attention deficits in patients with different kinds of vestibular disorders ([8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24]; see [25], [26], [27] for reviews). Given the severity of the symptoms in some vestibular disorders such as Meniere’s disease, it is possible that cognitive dysfunction is an indirect consequence of symptoms such as vertigo. However, studies of patients with chronic vestibular loss, and without vertigo, have still demonstrated spatial memory impairment [15], even 5–10 years after complete bilateral vestibular loss [12].
Numerous studies in animals have also demonstrated that unilateral or bilateral lesions of the vestibular system disrupt spatial memory [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45]. The effects of bilateral vestibular loss (bilateral vestibular deafferentation, BVD) are particularly profound and have been shown to last for at least 14 months [28]. These spatial memory deficits are not simply the result of an inability to move, since these animals are hyperactive. However, regression analyses show that the extent of the spatial memory deficits cannot be predicted from the degree of hyperactivity [28]. Neurophysiological studies have shown that BVD causes an impairment of the function of place cells [46], [47] and theta rhythm [44], [48], [49] in the hippocampus, which are related to spatial memory. Humans with bilateral vestibular loss have even been demonstrated to exhibit a bilateral atrophy of the hippocampus of approximately 17% [12].
The link between vestibular dysfunction and anxiety/depression is well recognised clinically and is believed to be due to more than living with the burden of a vestibular disorder [50], [51], [52], [53], [54], [55], [56], [57]. Not only do patients with vestibular disorders frequently experience symptoms of anxiety and depression, but those with anxiety and depression can experience vestibular disorders [58], [59], [60]. There appears to be a complex, two-way interaction between vestibular function and affective state, which may be partly related to the contribution of the vestibular system to the control of autonomic function (e.g., heart rate, blood pressure, respiration) [50], [51], [52], [53], [54], [55], [56], [57]. This kind of evidence suggests that vestibular impairment may cause a multitude of changes in cognition, emotion and personality, which is consistent with some evidence that vestibular disease is associated with unusually high rates of depersonalization/derealization symptoms, which include difficulty focussing attention and thoughts seeming blurred (e.g., [16], [17]).
Whether the cognitive deficits associated with vestibular damage are limited to spatial memory impairment is unclear. Some human studies have reported that other aspects of memory and general intelligence are normal [12]. Some animal studies using BVD have reported deficits in object recognition memory [61] and more recently, using the 5 choice serial reaction time task (5-CSRTT), substantial attentional deficits [62], [63]. In these latter studies, the percentage of correct responses was significantly less in the BVD group compared to sham controls, and the percentage of incorrect responses greater; however, there was no significant difference between the two groups in the number of omissions, indicating once again that the performance deficits for the BVD rats were not due to an inability to respond.
Section snippets
Dyscalculia and vestibular function
Amongst these reports of cognitive deficits that are ostensibly independent of spatial memory, a few researchers have reported a link between vestibular function and dyscalculia, the inability to manipulate numbers [19], [24]. Yardley et al. [24] investigated the effects of having to continuously monitor body position during vestibular stimulation, on the ability to perform mental arithmetic. Arithmetic performance was significantly degraded in this dual task situation. Risey and Briner [19]
Hypothesis
Activation of the vestibular system contributes to numerical discrimination and memory, and the response of neurons in the brain that encode number, by providing head movement and position information that is necessary for normal spatial memory. Consequently, artificial activation or inactivation of the vestibular system will disrupt the normal influence of this sensory system on numerosity. Dyscalculia in patients with vestibular dysfunction is likely to be a result of impaired spatial memory
Conflict of Interest
None declared.
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Impaired math achievement in patients with acute vestibular neuritis
2017, NeuropsychologiaCitation Excerpt :Second, we were also interested whether PVD results in basic problems in processing the magnitude of numbers. Impaired performance in a number processing task would support the hypothesis of Smith (2012) since it is reflects a key aspect of dyscalculia. For this reason, we used the number Stroop task, which typically produces abnormal results in children and adults with impaired numerical cognition (e.g., Algom et al., 1996; Ashkenazi et al., 2009; Girelli et al., 2000; Rubinsten and Henik, 2005; Rubinsten et al., 2002).
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2015, The Rat Nervous System: Fourth EditionVestibular insights into cognition and psychiatry
2013, Brain ResearchCitation Excerpt :Selective serotonin reuptake inhibitors (SSRIs) are efficacious in the treatment of vertigo (Johnson, 1998) and SSRI withdrawal is associated with vestibular manifestations (i.e. dizziness) (Coupland et al., 1996). In relation to dopamine, dopamine (D2) receptors have been identified in neurons of the medial vestibular nucleus and the lateral vestibular nuclei (Smith and Darlington, 1994) and meaningful levels of dopamine have been detected in a region of the vestibular nuclei (Cransac et al., 1996). There is also evidence to suggest that dopamine might exert a modulatory action on the vestibular system, either by a direct action on the vestibular neurons or by modulation of GABAergic transmission (Vibert et al., 1995).
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