An fMRI Study on the Separate Mechanisms of Visual and Tactile Memory
An fMRI Study on the Separate Mechanisms of Visual and Tactile Memory An overview of Tactile Memory
Tactile memory is part of sensory memory systems and it is the recollection of information acquired via touch. It is one of the primitive sensory codes that are used as interacting familiar objects. It is not only important to interact with familiar objects but it is also necessary to interact with novel objects with similar size. Traces of tactile information is similar to iconic memory in terms of duration of the trace since it lasts for a short time and it is vulnerable to decay after almost two seconds (Gallace, &Spence, 2009). One of the earliest experimental studies on tactile memory was conducted by Bliss, Crane, Mansfield, and Townsend (1966). In this study, they investigated the characteristics of immediate recall for brief tactile stimuli applied to the hand. The results obtained showed a haptic memory store remarkably similar to the visual memory store. Similar to tests of visual sensory memory, it was also found that haptic memory performance was significantly improved with the use of partial report procedures. In a recent study, Gallace and Spence (2009) also verified these findings. According to Bliss and colleagues, the difference between partial report and whole report is the result of a sensory form of memory for passively presented tactile stimuli with a high capacity and short duration. Furthermore, Gilson and Baddeley (1969) argued that memory for stimuli applied to the skin is resilient for approximately ten seconds after removal of the stimulus, even when the individual is engaged in tasks that inhibit verbal rehearsal. After this delay, the memory trace becomes vulnerable to forgetting as it decays from the haptic memory store and begins to rely on a more central memory store. Although tactile memory representations can be thought as similar to visual representations in nature but there are significant differences between these two different memory systems in terms of processing and neural anatomy. Easton, Srivinas, and Greene (1997) showed that there is an innate difference between visual and tactile memory representations. In their study, they presented their participants with an object either in visual or tactile forms. In the study, the participants viewed a sphere but they could not touch it. After that, the participants were given a similar shape but they could not see it. The results of the study indicated that the participants’ performance was worse as they were judging size differences in visual form compared to that in tactile form. It is suggested that this is because the participants’ processing in visual form resulted in more variance in terms of object size due to influences, such as perspective and distance. Nero-anatomy of Tactile Memory
Tactile memory is widely organized in the somatosensory cortex. The information signals received by body surface goes to the areas that are close together on the brain surface. Various areas of the parietal lobe are responsible for contributing to several aspects of tactile memory. Memory for the features of a stimulus including its roughness, spatial density, and texture result in activation of the parietal operculum. On the other hand, features of a stimulus, such as size and shape are detected by touch receptors in the skin. These signals are maintained in the anterior part of the parietal lobe. In addition to features of the stimulus, memory for spatial information such as the location of stimulusactivates the right superior parietal lobule andtemporoparietal junction (Gallace, &Spence, 2008). There are several studies investigating neural correlates of tactile memory. In one study, Harris, Harris, and Diamond (2001) assess the contribution of topographically organized neural areas to tactile working memory. In...