User:MJEngland/sandbox

Overview:
Body part as an object (BPO) pantomimes occur when a person substitutes a part of their body - usually arms, fingers, or hands - to be part of an object they are miming (Goodglass & Kaplan, 1963). Pantomimes are representational gestures, meaning they are used to convey a message to others without the use of speech (Hostetter & Skirving, 2011; Critchley, 1973; Goodglass & Kaplan, 1963). A commonly used example of BPO pantomiming is demonstrated by an individual using their finger to represent a toothbrush while acting out brushing their teeth (Overton & Jackson, 1973).

In studying gestures from a psychological, psycholinguistic, and/or neuropsychological context, pantomimes can be distinguished by how they are carried out. For example, BPO pantomimes are differentiated by the insertion of a body part to help represent the object itself (Goodglass & Kaplan, 1963). Conversely, Imaginary object (IO) pantomimes occur when a person mimes the use of an object as though the object were actually present. Using a similar example to above, an IO pantomime occurs as an individual pretends to brush their teeth by positioning the hand and fingers as though the toothbrush were actually in their hand: they are pretending the object is actually present (Overton & Jackson, 1973)

What makes this topic notable? (Jeff, I was wondering if you wanted to incorporate a quick blurb here because I think your sections cover that quite well! If not, I certainly don’t mind)

Pantomimes: BPO and IO
BPO pantomimes are generally seen more in young children (3-5 years old) and those with brain damage (O’Reilly, 1995). There are many theories as to why BPO may be prevalent in these populations. This includes disruptions in the conceptual or temporal-spatial stages in the process of learned gestures (Rothi, Mack, Varfaellie, Brown & Heilmann, 1997), an impairment of conveying hand-posture of tool use (Raymer, Maher, Foundas, Heilman, and Rothi, 1997), and a poor representation of an external objects (Haaland & Flaherty, 1984; Overton and Jackson 1973; O’Reilly, 1995). IO pantomimes are seen as much more complex than BPO pantomimes because they must have a strong mental representation of the object to be used and understood. An individual cannot garner any supportive information from the environment, and must know and understand the properties of the object to manipulate it as though it is in use, even though it is not physically present (Suddendorf, FletcherFlinn, & Johnston, 1999).

Examples of Models Explaining Gestures
There have been many models attempting to explain how gestures are related to semantic concepts, such as imagery and speech. The Sketch Model relates semantic concepts and gestures to one another. It posits that gestures and speech have the common purpose of communication, and thus are represented at the same conceptual level. The function of gestures are then to enhance access to mental imagery (de Ruiter, 2000). Motor movement, while gesturing, has also been related  to phonological encoding (Kraus et. al, 2000);  therefore, gestural movements may prompt access to word forms and help the speaker convey their intent to others. Significantly, this model can only be generalized when gestures and their consequent speech have a meaningful relationship with each other. Overall, this theory suggests that difficult speech, such as describing motor and spatial information, will increases the amount of representational gestures produced by a speaker. Studies have supported this model through unplanned speech producing more gestures, the description of difficult figures producing more gestures than simpler figures, and a greater amount of gestures produced when participants have the freedom to say whatever they would like instead of following a script (Hostetter & Skirving, 2011).

Additionally, there are many studies that have shown increased gesture production is dependant on the availability and strength of an imagery representation (Hostetter & Skirving, 2011). Most recently, the Gesture as Simulated Action (GSA) theory has become prominent; it focuses on the role of mental imagery in increasing an individual's rate of gestures. GSA posits that imagining an object or event stimulates the same brain areas - the motor and visual cortices - involved in using or viewing objects and events, and thus facilitates the production of a representational gesture (Kossyln, 2005). Therefore, when objects are thought of using mental or visual imagery, more gestures should be produced. On the other hand, if an object is thought of only through its verbal representation, there should be fewer gestures present (Hostetter & Skirving, 2011).

Tool-Use and Gestures
Tool-use is the manipulation, or use, of an object using the hands (Lewis, 2006). It is one of the many skills that separate humans from animals. There are two factors used to explain tool-use in humans. First of all, part of tool-use knowledge is physical, meaning that it involves the actual manipulation of an object. The other type of knowledge is conceptual: using the physical (or active) knowledge of tool-use to add to the mental representation of the tool. Action schemas explain how we develop motor skills and performance of many complex motor-activities. Essentially, the more an object is manipulated and used, a greater schema is developed in the brain. Therefore, increased object use gives us a greater understanding of the object, which then facilitates our understanding of the object independent of its context. The strength of an action schema is significant in studying apraxia and BPO pantomimes, because there appears to be a disruption in the context of an object: an individual may understand the function of an object, but experiences difficulty using the object out of its context, or when it is not physically present. (Lewis, 2006)

There have been many studies relating activated brain areas to tool-use, in both physical object manipulation and pantomimes. Meta-analyses have found that tool-use is largely lateralized in the left-hemisphere of the brain and independent of handedness (Lewis, 2006). Specifically, the brain region which showed the greatest activity was the left superior parietal lobule. Other areas that showed significant activity was bilaterally in both the ventral and dorsolateral premotor cortex, areas by the inferior parietal lobule, and tissue around the medial temporal gyrus. Furthermore, even when object-use was imagined, activation was found to be largely lateralized in the left hemisphere and was very similar to the brain activation in actual tool-use and pantomiming. The only significant difference was additional activation in the left occipito-parietal region.

Interestingly, viewing tools potentiates motor activity related to the specific tool-use. This phenomenon is different from other classes of objects, and indicates that tools are not viewed just based off what they are, but also what they actually do. In just viewing tools, activation of left lateralized areas are very similar to the use/pantomiming areas as noted above. These areas include the ventral premotor cortex, left inferior frontal gyrus and some parietal areas. The main difference is that tools being used elicit greater activation in ventral brain regions, and decreased activation in primary motor areas. Additionally, there were very similar areas of activation in naming tools and viewing tools. There were other areas of activation in the left hemisphere, possibly reflecting the lateralization of language (Lewis, 2006).

Differential brain activation has been compared between the us of either IO or BPO pantomimes (Ohgami, Matsuo, Uchida, & Nakai, 2006). The IO pantomime activity was largely lateralized in the left hemisphere, namely in the bilateral supplementary motor areas, cingulate gyrus, left premotor areas, left superior parietal lobule, and the left middle and inferior frontal gyri. The BPO pantomimes activated areas bilaterally in the supplementary motor areas, cingulate gyrus, premotor areas, SMG and the left inferior and middle frontal gyri, and the left medial temporal gyri. The main difference observed was that IO pantomime activation was left-hemisphere lateralized and BPO pantomime activation was bilateral. These results imply that BPO pantomimes actually show greater activation than IO pantomimes (despite the prevailing conception that they are simpler), and that BPO involves the right hemisphere as well as the left hemisphere. These results could be extended as an explanation of why apraxic brain damage - usually found in left-hemisphere - leads to BPO production (Ohgami et. al). This may be an indication that apraxic’s utilize their right-hemisphere in lieu of their left-hemisphere damage, and therefore produce more BPO pantomimes (Ohgami et. al).