Friday, September 18, 2009
Observation of tool use activates specific brain area only in humans
The discovery that a species other than human has the ability to use tools has, quite frankly, lost its novelty. Just look at the New Caledonian crow. If trained properly, it can utilize up to three different tools sequentially to reach for a target food reward (Wimpenny et. al, 2009). It does this by first picking up a stick-like tool with its beak. It then uses this tool to retrieve a second tool which is then used to retrieve a third tool. Finally, the third tool is used to successfully retrieve the food (sadly, I couldn't even do it using two).
An earlier study conducted by Taylor et. al (2007) demonstrating how the New Caledonian crow utilizes two tools in sequential order to retrieve a food reward:
If a mere "bird brain" can manage to use tools in such a complex way what makes us so special? Is the human brain really that much more "evolved" in comparison to the brains of other animals?
A study by Peeters and colleagues published in this weeks Journal of Neuroscience may offer further clues to these questions. The researchers had a large cohort of human volunteers, untrained monkeys, and trained monkeys watch videos demonstrating hand actions and actions performed using simple tools. This led to the activation of bilateral occipitotemporal, intraparietal, and ventral premotor cortices in all groups.
However, they found that after watching the simple tool use video a rostral sector of the left inferior parietal lobule known as the left anterior supra marginal gyrus (aSMG) was activated in humans ONLY. This is a curious finding because one would think that the trained monkeys would also show similar activations in this particular area of the brain. So what does this all mean?
According to the results the human aSMG is only activated during the observation of hand grasping and not during static representation of tool images, indicating the aSMG's involvement in the cognitive aspect of tool use. The aSMG associates the intended use of the tool with the results obtained by using it.
The authors suggest that the rostral part of the IPL is a new brain area exclusive to humans and functions to understand tool actions. They note that this is indeed a "fundamental cognitive leap that greatly enlarged the motor repertoire of humans and, therefore, their capacity to interact with the environment".
They go on to state that even though monkeys know how to use tools it doesn't necessarily imply an understanding of the abstract relationship between the tools being used and the goals that can be achieved by using them. Boo-yah! In your face monkeys! It seems like we really are special...for now.
Here's a video of the fuzzy haired critters using anvils and hammers to break open some delicious snacks.
I also provide a link to Wired's Clever Critters: 8 Best Non-Human Tool Users
Wimpenny JH, Weir AA, Clayton L, Rutz C, & Kacelnik A (2009). Cognitive processes associated with sequential tool use in New Caledonian crows. PloS one, 4 (8) PMID: 19654861
Peeters R, Simone L, Nelissen K, Fabbri-Destro M, Vanduffel W, Rizzolatti G, & Orban GA (2009). The representation of tool use in humans and monkeys: common and uniquely human features. The Journal of neuroscience : the official journal of the Society for Neuroscience, 29 (37), 11523-39 PMID: 19759300