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Baars and Gage: Cognition, Brain, and Consciousness

Study Guide Solutions

Chapter 9: Learning and Memory

  1. What is a definition of memory? What kinds of memory performance are humans best at? Provide everyday examples.

Memory can be defined as a lasting representation that is reflected in thought, experience, or behavior. Learning is the acquisition of such memories. Human memory is exceptionally good in dealing with complex, ill defined, and novel challenges, the kinds of challenges that people have to deal with in the real world (see pages 255-256). Humans are adept at implicitly – unconsciously – detecting a pattern or scheme of events; typically implicit learning occurs prior to explicit recognition of a method with which to solve problems or remember information. One example of implicit memory performance has been provided through experiments where subjects are asked to read a list of words and then are called back days or weeks later and given an explicit memory test to see how many of the words were still recalled. Typically, especially when the time delay is long enough, there are not many words that are explicitly remembered. If a test is made of implicit memory, using a priming technique described on page 260, it reveals that many more words are still available in implicit – unconscious – memory.

  1. What are some brain areas believed to serve human memory?

Memory storage is believed to involve very widespread synaptic alterations in many parts of cortex (see Chapter 3 for a discussion of the neural bases for learning and memory). Specific regions involved in memory are in the medial temporal lobe (MTL) and include the hippocampi and surrounding tissues (see pages 256-257 and Figures 9.1, 9.2, and 9.3). The MTL is a hub with widespread connections to visual, auditory, and somatosensory sensory regions as well as regions that support emotional, executive, and motor memory functions.

  1. What is a central difference between ‘explicit’ and ‘implicit’ memory? Provide some everyday examples of each.

The central difference between explicit and implicit memory is that explicit memory, as its name implies, is memory that you are aware of: you are explicitly aware of remembering items or events and are also aware of their retrieval. Implicit memory is not accompanied by conscious awareness: the memory’s existence is inferred only from the effects it has on behavior. Implicit memories may be retrieved without an intention to remember: they just ‘come to mind’.

  1. How has the case of patient Clive Wearing informed about us about memory systems?

The case of Clive Wearing suggested that amnesia is selective – certain kinds of memory may survive while others are lost. In the case of Wearing, he is able to carry on a normal conversation so his memory for language use and social aspects of conversation is intact. He retains general world knowledge and has an extensive vocabulary. The central memory that Clive Wearing retains is his love for his wife, Deborah. The central memory loss is that he can no longer form new memories, he can neither learn nor remember specific events. Moments after having seen his wife Deborah, he has forgotten that she was there. The case of Clive Wearing provides evidence that memory is not unitary, but consists of different types of memory that may have differing brain localizations, and may be selectively damaged due to disease or injury.

  1. What brain areas were removed in the case of HM and what were his main deficits following surgery? Were any aspects of his memory left intact?

Both sides of the medial temporal lobe (MTL), including the hippocampi, were surgically removed from the brain of HM, (see page2 262-263 and Figure 9.7). As a result of the operation, HM could not remember any of the events of his life thereafter: no new memories can be formed: he has anterograde amnesia. He no longer recognizes himself in the mirror because he has aged since his surgery. He does retain some memories of his early life and for many years could find his way to his parents’ house. However he cannot recall events that occurred shortly before the surgery: he has retrograde amnesia. Not all aspects of memory were damaged by his surgery: he has an intact short-term memory, he has retained his general world knowledge, and he can carry on an intelligent conversation about the immediate present. Like Clive Wearing, social and language information was retained.

  1. Briefly, what brain areas are thought to be involved during: a) memory formation, b) memory integration, and c) memory consolidation?

Immediately, new events or memories are encoded in improved synaptic connections between billions of neurons in the neocortex (see page s 269-272 and Figure 9.15). This information is then sent to the medial temporal lobe (MTL). The neocortex and MTL are also active during memory integration. During memory consolidation, the process of transforming temporary memories to permanent storage, the MTL is active. During memory retrieval, MTL and the neocortex are again both activated (see Figure 9.16).

  1. What are the key differences between episodic and semantic memory? Are they always separable? What experimental paradigm is typically used to separately tap into these memory processes?

Episodic and semantic memory are two forms of declarative (conscious) memory (see pages 274-276 and Figure 9.18). Episodic memory refers to memories that have a specific source in time, space, and life circumstances – in other words, they correspond to an episode (see Figure 9.19). Episodic memories are often autobiographical in nature: we can think back to last weekend, last summer, our 10th birthday – specific events that we can explicitly recall.

Semantic memory involves facts about the world, ourselves, and other knowledge that we share with a community (see Figure 9.20). These memories are independent of the time and space when and where they were acquired: they are not directly related to an episode. For example, semantic memory may contain general information about birthdays and birthday parties but will be separable from specific memories of your last birthday.
Are episodic and semantic memories always distinct and separable? One hypothesis is that episodic memories turn into semantic memories over time (see page 277 and Figure 9.22). Specifically, semantic memories may be the neocortical ‘residue’ of many episodic memories. For example, all of the episodic memories formed during one’s own birthday parties and other birthday celebrations may combine to form a general, knowledge-based rather than episode-based memory for ‘birthdays’.
Experimentally, investigations of episodic and semantic memory use a ‘remember-know’ paradigm (see Figures 9.19 and 9.20). A simple example of the ‘remember-know’ procedure is to ask participants to study a list of words. After a delay, the participants are provided with a longer list of words: some are words that the participants had studied and some are new. The participants are asked to mark the words that they studied and to rate their recall for the words into two categories: remember – they have a specific memory of having studied the word, or know – they have a general feeling of knowing that the word was studied rather than a specific conscious recollection. This experimental paradigm may also be used in imaging studies to investigate which brain areas are active during remember vs. know processing (see Figure 9.21). It can also be used with patients to investigate how intact their episodic and semantic memory systems are following brain damage or disease.

  1. How does dividing one’s attention affect memory encoding? Provide everyday examples of the effects of divided attention on memory formation.

Learning -- memory encoding -- works best when you pay attention. Being distracted while trying to learn – called divided attention in cognitive psychology terms – impairs retention of new items learned. Successful encoding requires a level of attention and, presumably, consciousness. How does divided attention impair memory encoding? This question is still being answered by memory scientists. One hypothesis is that the deeper processing required to learn takes time to complete and divided attention limits the time allotted for encoding. Another hypothesis is that consciousness or awareness is a necessary contributor to memory encoding. Under divided attention situations, one may not be fully conscious of the material being encoded.
An everyday example of divided attention: if you are studying for an exam and have your textbook and lecture notes in front of you – but you also have your laptop on and your instant messaging open, you are playing some songs you have just downloaded, and you have a group of students at the next table talking and laughing – you are under a situation of divided attention. Although some students seem to learn well under some situations of divided attention, most will be distracted by the onslaught of multiple attention-attracting items in their immediate vicinity.

  1. What role does the prefrontal cortex (PFC) play in working memory? How is it typically tested in primate studies?

Results of non-human primate and human studies combine to implicate the PFC’s role in active maintenance of working memory information (see pages 279-283). Much of this work has focused on the dorsolateral PFC (DL-PFC) using a ‘delayed match to sample’ paradigm with macaque monkeys (see Figure 9.24). In this paradigm, the macaque is trained to delay responding to a stimulus, he must keep it in mind until the time when he may respond. Single unit recordings are typically made during the presentation of the stimulus, the delay period, and the response period in order to determine which neurons are active during these three time periods. The neurons that are activated during the delay period are thought to support active maintenance of working information. Related findings have been reported in neuroimaging studies with humans using a similar experimental paradigm (see Figure 9.25).

  1. Are there different types of working memory? Briefly, what is the evidence in support of multiple working memory systems? What are arguments again this theory?

The notion of multiple types of working memory has developed from experiments where subjects are asked to rehearse information and at the same time are provided with a task that is meant to distract or disrupt this active rehearsal. The concept of a verbal working memory comes from classic work performed by Baddeley and others, who found that asking a subject to rehearse verbally presented information while repeating aloud a simple utterance (such as ‘the’) disrupted the rehearsal process. The same repetitive speech task had a diminished effect when the subject was rehearsing a visuospatial pattern. These and related findings provided evidence that working memory for verbal information and visuospatial information were separable. This work is ongoing, see Figure 9.27 for neuroimaging findings regarding brain areas that serve working memory systems.

  1. What is metacognition? What brain areas are thought to be involved in metacognition?

Metacognition is defined as the ability to know our own cognitive functions, and to be able to use that knowledge (see pages 286-287). For example, Clive Wearing is aware that something is terribly wrong but he has no idea what it is: he writes to his wife “I’ve just woken up for the first time”. Wearing must have some metacognitive conception of his predicament. Not all patients are aware of their deficits: they are lacking metacognitive function. Brain areas thought to be involved in metacognition include regions in the prefrontal cortex.

  1. Are there any hemispheric differences in memory retrieval? Briefly describe the evidence for and against this idea.

Memory retrieval may be lateralized to one hemisphere or the other based on the nature of the material being processed (see pages 287-288). For example there is evidence that maintenance of verbal information activates regions in the left hemisphere in parietal cortex and the ventrolateral prefrontal cortex (VL-PFC), while maintenance of non-verbal information tends to activate right hemisphere sites. Both the VL-PFC and the medial temporal lobe have been found to exhibit hemispheric asymmetries in long-term memory encoding.
The question of whether the hemispheres perform differing processes in memory retrieval is complex: investigating this question involves using differing types of stimuli and many paradigms include tasks: do hemispheric differences reflect lateralization of memory retrieval processes? Or do they reflect lateralization of stimulus processing or task-related mechanisms? This remains a largely open question.
Tulving and colleagues propose that, in general, learning is associated with greater involvement of the left PFC, while retrieval shows greater involvement of the right PFC (see Figure 9.30). Other scientists have proposed that this hemispheric bias holds for episodic memories but that in semantic memory, both learning and retrieval seem to be more dependent on left hemisphere mechanisms.
While this research is ongoing, the data at present indicate that there are hemispheric differences that correspond to the type of material being retrieved as well as the type of memory that is being retrieved.

© Elsevier Ltd 2007

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