Approaching objects cause confusion in patients with Alzheimer's disease regarding their direction of self-movement

Department of Neurology, University of Rochester Medical Centre, 601 Elmwood Avenue, Rochester, NY 14642-0673, USA.
Brain (Impact Factor: 9.2). 09/2010; 133(9):2690-701. DOI: 10.1093/brain/awq140
Source: PubMed

ABSTRACT Navigation requires real-time heading estimation based-on self-movement cues from optic flow and object motion. We presented a simulated heading discrimination task to young, middle-aged and older adult, normal, control subjects and to patients with mild cognitive impairment or Alzheimer's disease. Age-related decline and neurodegenerative disease effects were evident on a battery of neuropsychological and visual motion psychophysical measures. All subject groups made more accurate heading judgements when using optic flow patterns than when using simulated movement past earth-fixed objects. When both optic flow and congruent object were presented together, heading judgements showed intermediate accuracy. In separate trials, we combined optic flow with non-congruent object motion, simulating an independently moving object. In the case of non-congruent objects, almost all of our subjects shifted their perceived self-movement to heading in the direction of the moving object. However, patients with Alzheimer's disease uniquely indicated that perceived self-movement was straight-ahead, in the direction of visual fixation. The tendency to be confused by objects that appear to move independently in the simulated visual scene corresponded to the difficulty patients with Alzheimer's disease encountered in real-world navigation through the hospital lobby (R(2) = 0.87). This was not the case in older normal controls (R(2) = 0.09). We conclude that perceptual factors limit safe, autonomous navigation in early Alzheimer's disease. In particular, the presence of independently moving objects in naturalistic environments limits the capacity of patients with Alzheimer's disease to judge their heading of self-movement.

9 Reads
  • Source
    • "Observing a relationship between the function of the septohippocampal system and self-movement cue processing in rats provides a translational model to investigate the factors that contribute to wandering behavior observed during the progression of DAT. For example, recent work has demonstrated deficits in self-movement cue processing observed during the progression of DAT that was related to disruptions in spatial orientation (Tetewsky and Duffy 1999; Kavcic et al. 2006; Mapstone and Duffy 2010). The combination of selective lesion techniques and behavioral tasks that can dissociate the type of cues used to guide movement and mnemonic function provides the foundation necessary to model disruptions in spatial orientation associated with neurodegenerative disorders. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Degeneration of the septohippocampal system is associated with the progression of Dementia of the Alzheimer's type (DAT). Impairments in mnemonic function and spatial orientation become more severe as DAT progresses. Although evidence supports a role for cholinergic function in these impairments, relatively few studies have examined the contribution of the septohippocampal GABAergic component to mnemonic function or spatial orientation. The current study uses the rat food-hoarding paradigm and water maze tasks to characterize the mnemonic and spatial impairments associated with infusing GAT1-Saporin into the medial septum/vertical limb of the diagonal band (MS/VDB). Although infusion of GAT1-Saporin significantly reduced parvalbumin-positive cells in the MS/VDB, no reductions in markers of cholinergic function were observed in the hippocampus. In general, performance was spared during spatial tasks that provided access to environmental cues. In contrast, GAT1-Saporin rats did not accurately carry the food pellet to the refuge during the dark probe. These observations are consistent with infusion of GAT1-Saporin into the MS/VDB resulting in spared mnemonic function and use of environmental cues; however, self-movement cue processing was compromised. This interpretation is consistent with a growing literature demonstrating a role for the septohippocampal system in self-movement cue processing.
    Brain Structure and Function 08/2012; 218(5). DOI:10.1007/s00429-012-0449-7 · 5.62 Impact Factor
  • Source
    • "The authors considered that the failure of cue integration was due to the loss of cortico-cortical connectivity in the parietal visual association cortex. Furthermore, neuropsychological studies reported impairments in visuospatial perception including the perception of OF and self-movement in patients with MCI [75] [76] [77]. Thus, a large number of studies show impairment in the higher level dorsal stream in AD and MCI. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Visuospatial dysfunction including defects in motion perception in Alzheimer's disease (AD) and mild cognitive impairment (MCI) are clues to search for potential in vivo biomarkers. In this review, we focus on the clinical relevance of non-invasive neurophysiological findings in event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI) to assess visual dysfunction in AD and MCI. We first summarize the current concept of the parallel visual pathways in primates and humans. Next, we outline the results of previous electrophysiological and fMRI studies on visual function in AD and MCI. Finally, we present the recent findings of our systematic ERP and fMRI approach to visual perception in AD and MCI. Our overview strongly indicates that visual impairments in patients with AD and MCI are mainly caused by dysfunction in higher-level parallel visual pathways. In particular, a deficit in ventro-dorsal stream function related to optic flow perception is responsible for the earliest and most prominent visual symptoms in MCI. Therefore, we conclude that ERP and fMRI measurements for visual perception can be used as in vivo biomarkers for early functional brain changes in MCI and AD patients.
    Journal of Alzheimer's disease: JAD 03/2012; 31:S137-54. DOI:10.3233/JAD-2012-112093 · 4.15 Impact Factor
  • Source
    • ") but are uniquely confounded by nonmatched heading cues, always seeing them as straight ahead self-movement regardless of the heading direction in the stimuli (Mapstone and Duffy 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: We presented naturalistic combinations of virtual self-movement stimuli while recording neuronal activity in monkey cerebral cortex. Monkeys used a joystick to drive to a straight ahead heading direction guided by either object motion or optic flow. The selected cue dominates neuronal responses, often mimicking responses evoked when that stimulus is presented alone. In some neurons, driving strategy creates selective response additivities. In others, it creates vulnerabilities to the disruptive effects of independently moving objects. Such cue interactions may be related to the disruptive effects of independently moving objects in Alzheimer's disease patients with navigational deficits.
    Cerebral Cortex 06/2011; 22(1):201-8. DOI:10.1093/cercor/bhr115 · 8.67 Impact Factor
Show more


9 Reads
Available from