Navigation-related structural change in the hippocampi of taxi drivers

Abstract

Structural MRIs of the brains of humans with extensive navigation experience, licensed London taxi drivers, were analyzed and compared with those of control subjects who did not drive taxis. The posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects. A more anterior hippocampal region was larger in control subjects than in taxi drivers. Hippocampal volume correlated with the amount of time spent as a taxi driver (positively in the posterior and negatively in the anterior hippocampus). These data are in accordance with the idea that the posterior hippocampus stores a spatial representation of the environment and can expand regionally to accommodate elaboration of this representation in people with a high dependence on navigational skills. It seems that there is a capacity for local plastic change in the structure of the healthy adult human brain in response to environmental demands. O ne important role of the hippocampus is to facilitate spatial memory in the form of navigation (1). Increased hippocampal volume relative to brain and body size has been reported in small mammals and birds who engage in behavior requiring spatial memory, such as food storing (2). In some species, hippocampal volumes enlarge specifically during seasons when demand for spatial ability is greatest (2, 3). In the healthy human, structural brain differences between distinct groups of subjects (for example, males and females, ref. 4, or musicians and nonmusicians, ref. 5) have been documented. From existing studies, it is impossible to know whether differences in brain anatomy are predetermined or whether the brain is susceptible to plastic change in response to environmental stimulation. Furthermore, although lesion work (6, 7) and functional neuroimaging work (8) confirm the involvement of the human hippocampus in spatial memory and navigation, there is still debate about its precise role. Given the propensity of lower mammalian͞avian hippocampi to undergo structural change in response to behavior requiring spatial memory (2, 3), the present study addressed whether morphological changes could be detected in the healthy human brain associated with extensive experience of spatial navigation. Our prediction was that the hippocampus would be the most likely brain region to show changes.Taxi drivers in London must undergo extensive training, learning how to navigate between thousands of places in the city. This training is colloquially known as ''being on The Knowledge'' and takes about 2 years to acquire on average. To be licensed to operate, it is necessary to pass a very stringent set of police examinations. London taxi drivers are therefore ideally suited for the study of spatial navigation. The use of a group of taxi drivers with a wide range of navigating experience permitted an examination of the direct effect of spatial experience on brain structure. In the first instance, we used voxel-based morphometry (VBM) to examine whether morphological changes associated with navigation experience ...

Strategy‐based reasoning training modulates cortical thickness and resting‐state functional connectivity in adults with chronic traumatic brain injury

“…We observed (1) nonmonotonic changes in the bilateral DLPFC, L SCG, R DPFC, and R AMPFC, (2) monotonic increases in the R POCG and R OCPL, and (3) monotonic decreases in the L PRCG, R MT+, and R APFC. Although the majority of the previous studies reported increases in cortical thickness or gray matter volume (Valkanova, Eguia Rodriguez, & Ebmeier, 2014), differences in directionality of cortical thickness and cortical volume changes across brain regions were also reported in several previous studies (Draganski et al., 2006; Maguire et al., 2000; Metzler‐Baddeley et al., 2016; Taubert et al., 2010). These diverse temporal trajectories of cortical thickness in both present and in previous studies demonstrate the complexity of brain plasticity.…”

“…While changes in morphometry following training can confirm that the adjustment of behavior modulates brain structure, the temporal patterns of training‐induced changes in morphometry are often complex. As such, the directionality of these changes has varied across previous studies (Draganski et al., 2006; Maguire et al., 2000; Metzler‐Baddeley, Caeyenberghs, Foley, & Jones, 2016; Taubert et al., 2010). RsFC can complement morphometry to better understand the complex patterns of changes occurring after training.…”

Evidencing a place for the hippocampus within the core scene processing network

“…While studies in rodents highlight the HC as critical for spatial navigation and allocentric spatial processing, as evidenced by the presence of place‐selective cells in HC [O'Keefe and Nadel, 1978] and spatial memory deficits following HC lesions [Morris, 1984], the notion that the human HC is involved in scene processing remains controversial [Suzuki, 2009]. While the human HC may be important for navigation [Ekstrom et al, 2003; Maguire et al, 2000; Suthana et al, 2009], its recruitment across a range of mnemonic and perceptual scene processing tasks is indicative of a broader role in scene cognition. Here, too, we localised HC using a working memory task, thus complementing previous studies that find evidence for HC recruitment across a range of cognitive tasks.…”

Studying neuroanatomy using MRI

“…The study of brain plasticity with MRI provides an illustrative example. The early identification of altered "concentration" of hippocampal grey-matter (as measured by VBM) in London taxi drivers suggested that the processes of learning and memory, so long studied in animal models, might be detectable by MRI in humans 54 . Additional evidence came from studies showing that teaching adults how to juggle altered grey-matter concentrations in the visual and parietal cortex 55 , a change that occurred in as quickly as seven days 56 , and was accompanied by changes in water diffusion in underlying white matter 57 .…”