Hassabis Phd: Imagination Uses Spatial abilities

Source: Hassabis PhD dissertation, 2009

Episodic memory recall is widely agreed to be a reconstructive process, one that is known to be critically reliant on the hippocampus. I therefore hypothesised that the same neural machinery responsible for reconstruction might also support ‘constructive’ cognitive functions such as imagination. 

 imagination simply becomes the flipside of memory where the goal now is to create something unfamiliar and new, rather than familiar, from the same set of building blocks. 

 this scene construction network might underpin other important cognitive functions besides episodic memory and imagination, such as navigation and thinking about the future. 

Consider an organism that, in their present situation, is confronted by several choices of what to do next. Being able to accurately and richly mentally simulate (Buckner & Carroll 2007) or construct what those possible future states might be like, before making the decision, would aid both the evaluation of the desirability of those outcomes and the planning processes needed to make them happen.

The applications of construction go beyond just planning for and anticipating possible future events (Atance & O’Neill 2001; Buckner & Carroll 2007; Emery & Clayton 2004; Schacter & Addis 2007). It forms the basis of imagination and possibly creativity, where constructions are envisaged that are not directly related to the future or the past, or to prediction per se, but for general problemsolving and invention purposes such as tool manufacture or art.

Viewed in this way imagination simply becomes the flipside of memory where the goal now is to create something unfamiliar and new, rather than familiar, from the same set of building blocks.

The building blocks of a memory are reassembled with the goal of transiently recreating a whole that seems coherent, familiar and self-relevant.

By contrast, the creative process attempts to connect these components together in new unfamiliar ways, the more creative the person the more unusual and lateral the connections they can make. But this is not enough; to be a Mozart, a Picasso or a Da Vinci one must also have good aesthetic judgment.

It is not sufficient to be able to just connect things in new ways. These connections must also make sense and be elegant in the context of the task domain e.g. aesthetic beauty in art, consumer preferences in business.

So the creative process can be summarised in three steps: (i) the acquisition of components through exposure to experiences – nothing is created in a vacuum, (ii) making novel connections between these components, and (iii) selecting the best fitting connections from amongst them.

This allows humans to be limitlessly creative and inventive even though constrained by a basic set of raw component elements gleaned over a lifetime of experiences.

… a second potentially dissociable dynamic integration function to the hippocampus. This facilitates the binding of online cortical information into a spatially coherent whole, a process that underpins scene construction and is key to the rich recollective experience that accompanies episodic memory recall. 

These two hippocampal roles, mnemonic and online spatial integration, are separable and dissociable, and can be engaged individually or in conjunction by different tasks, with the mnemonic role for declarative memory possibly time-dependent following consolidation (Squire et al. 2004).

For example, the following tasks all require the dynamic integration function: rich reliving of a remote episodic memory with a fully consolidated memory index, imagination of new experiences, and perhaps even scene perception. Whereas purely semantic tasks such as word-pair recall that do not require reliving only engage the mnemonic function. However, the re-experiencing of a recent memory or navigating in a recently learned location would engage both hippocampal functions

Excerpts that refer specifically to “imagination”

It is has been proposed that spatial context may act as the scaffold around which episodic memories are built. Given the hippocampus appears to play a critical role in imagination by supporting the creation of a rich coherent spatial scene

When imagining a new experience participants were explicitly told not to describe a remembered event or any part of one but rather to give free reign to their imaginations and create something new. They were also encouraged to ‘see the situation and setting in their mind’s eye’ as if they themselves were physically present, and to describe as many sensory and introspective details about the situation as they could.

To conclude, I have demonstrated that a distributed brain network, including the hippocampus, is recruited during both episodic memory recall and the visualisation of fictitious experiences. The present data provides evidence for the role of this brain network in scene construction, a critical process underpinning rich recollection, episodic future thinking and imagination.

Experiments 1 and 2 showed that the process of scene construction is a key component process that underpins both episodic memory and imagination.

The hippocampus plays an important role in scene construction by binding the disparate elements of a scene together into a coherent spatial context (see Chapter 4). But is it just about space or is this dynamic integrational role for the hippocampus (see Section 8.9) important for the binding of non-spatial elements? This question has it origins in the long-standing theoretical debate between the Cognitive Map Theory (see Section 2.5) and the Relational Theory (see Section 2.6) as to the special status or otherwise of space.

The results from the patient imagination study (Chapter 4) demonstrate that hippocampal patients are impaired at imagining new experiences. Moreover, this deficit seems to be driven by an inability to form spatially coherent representations of the  imagined scenes

The applications of construction go beyond just planning for and anticipating possible future events (Atance & O’Neill 2001; Buckner & Carroll 2007; Emery & Clayton 2004; Schacter & Addis 2007).

It forms the basis of imagination and possibly creativity, where constructions are envisaged that are not directly related to the future or the past, or to prediction per se, but for general problemsolving and invention purposes such as tool manufacture or art.

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