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. 1997 Sep 15;17(18):7103-10.
doi: 10.1523/JNEUROSCI.17-18-07103.1997.

Recalling Routes Around London: Activation of the Right Hippocampus in Taxi Drivers

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Free PMC article

Recalling Routes Around London: Activation of the Right Hippocampus in Taxi Drivers

E A Maguire et al. J Neurosci. .
Free PMC article

Abstract

Functional imaging to date has examined the neural basis of knowledge of spatial layouts of large-scale environments typically in the context of episodic memory with specific spatiotemporal references. Much human behavior, however, takes place in very familiar environments in which knowledge of spatial layouts has entered the domain of general facts often referred to as semantic memory. In this study, positron emission tomography (PET) was used to examine the neural substrates of topographical memory retrieval in licensed London taxi drivers of many years experience while they recalled complex routes around the city. Compared with baseline and other nontopographical memory tasks, this resulted in activation of a network of brain regions, including the right hippocampus. Recall of famous landmarks for which subjects had no knowledge of their location within a spatial framework activated similar regions, except for the right hippocampus. This suggests that the hippocampus is involved in the processing of spatial layouts established over long time courses. The involvement of similar brain areas in routes and landmarks memory indicates that the topographical memory system may be primed to respond to any relevant topographical stimulation; however, the right hippocampus is recruited specifically for navigation in large-scale spatial environments. In contrast, nontopographical semantic memory retrieval involved the left inferior frontal gyrus, with no change in activity in medial temporal regions.

Figures

Fig. 1.
Fig. 1.
Experimental design, two factors of interest:T, topographical memory; S, sequencing. A baseline task was also included.
Fig. 2.
Fig. 2.
Map illustrating the complex route recalled by a taxi driver during a route scan. Subjects did not see any maps; they were blindfolded throughout. His speech output for this task follows: Pick up on Grosvenor Square in Mayfair, drop off at Bank Underground Station, then at the Oval Cricket Ground… “Grosvenor square, I’d leave that by Upper Grosvenor Street and turn left into Park Lane. I would eh enter Hyde Park Corner, a one-way system and turn second left into Constitution Hill. I’d enter Queen Victoria Memorial one-way system and eh leave by the Mall. Turn right Birdcage Walk, sorry right Horse Guards Parade, left Birdcage Walk, left forward Great George Street, forward into Parliament Square, forward Bridge Street. I would then go left into the eh the Victoria Embankment, forward the Victoria Embankment under the Blackfriars underpass and turn immediate left into Puddledock, right into Queen Victoria Street, left into Friday Street, right into Queen Victoria Street eh and drop the passenger at the Bank where I would then leave the Bank by Lombard Street, forward King William Street eh and forward London Bridge. I would cross the River Thames and London Bridge and go forward into Borough High Street. I would go down Borough High Street into Newington Causeway and then I would reach the Elephant and Castle where I would go around the one-way system… . ” (end of scan).
Fig. 3.
Fig. 3.
Comparison of routes recall with landmarks recall. The activations are superimposed onto the averaged MRI scan of the 11 taxi drivers normalized to the same stereotactic space. The voxel of peak activation in the right hippocampus has been located here on relevant transverse sections. Other areas of significant activation in this comparison included the medial parietal region and the posterior cingulate gyrus.
Fig. 4.
Fig. 4.
A, Main effect of memory type displayed on a glass brain to show all areas of significant activation. Areas of increased rCBF during topographical memory compared with nontopographical memory. B, Main effect of sequencing displayed on a glass brain. Areas of increased activity when sequencing was required for correct memory recall are compared with memory recall for which no particular sequence of information was necessary.
Fig. 5.
Fig. 5.
Brain areas in which the effects of memory type and sequencing interacted are shown here on relevant transverse sections of the averaged MRI scan of the 11 taxi drivers. The interaction was determined by the following comparison [(routes–landmarks) − (film plots–film frames)]. Thearrow indicates the voxel of peak activation in the medial parietal region; the graph(bottom) shows the adjusted blood flow values at this voxel, revealing that the increased activity in this area is attributable primarily to sequencing in topographical memory (the two histogram bars for each task represent the two scans of the total 12 scans during which this task was performed).

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