Schizophrenia and working memory

Working Memory and Schizophrenia 1

Working Memory and Schizophrenia

Kelly Burke

27 October 2014


While schizophrenic persons only represent about one-percent of the total population (Bhatt, Laws and McKenna,

2010), the struggles that they face can have a significant impact on both themselves and on the unaffected members of

society. A majority of schizophrenic persons have difficulty with executive functioning, working, and episodic memory

(Allen et al., 2009), which could make maintaining an everyday routine especially challenging if not impossible. For

example, schizophrenics struggle to hold jobs that are considered simple and lower-maintenance by the average person,

such as working a cash register at a fast food restaurant, which leads them to have lower, if any, income. Thus, these

persons either become a full-time responsibility for their families, even in their adult and elderly years. If their families

are unable to support them, there is a high possibility that they may end up homeless or in jail, as the most severe of cases

may break laws without realizing or knowing that they are doing so; for example, a schizophrenic may walk out into the

middle of the road and cause an accident or a blockage because he or she was too absorbed in his or her own delusions to

notice what was going on around him or her. These are not, however, the only impairments associated with the disease.

Schizophrenic persons are characterized as having both impaired working memory (Mayer and Park, 2012) and

episodic memory (Caza, Dore, Gingras, and Rouleau, 2011), which, in part, explains the strangeness of some of their

delusions. Delusions, or persistently held false beliefs, are another hallmark of schizophrenia, although not all patients

experience the same level of delusions as others do (Bhatt et al, 2010). It has been questioned whether this odd way of

thinking is due to poor memory in general, as schizophrenics notoriously warp events to a greater degree than the average

person when recounting them later on (Caza et al., 2011). Four studies, however, point towards a different root for the

strangeness of the schizophrenic thought process: the schizophrenic population has a greater instance of false memories as

compared to the average (control) population. Therefore, their stories are not warped solely because they cannot clearly

remember which events transpired and how they unfolded, but because their false memories lead them to genuinely

believe that their narrative is correct despite its obvious flaws to outsiders. Perhaps, most importantly, is the root cause of

these false memories: impaired encoding processes. The following experiments suggest that errors during encoding,

which are more common in schizophrenics than in the average healthy population, lead to increased instances of false

memory. This review will present experimental data in support of the encoding errors as the root cause of false memory

as opposed to other factors, such as lower intelligence, faulty memory, and issues of recall.


Mayer and Park (2012) sought to establish working memory impairment, centered around faulty encoding, as the

root of false memories through the use of several spatial DRT tasks. 28 schizophrenic patients, 16 bipolar patients, 16

first-degree relatives of persons affected by schizophrenia, and 29 healthy controls that were demographic matches for the

schizophrenic group all participated in a spatial delayed response task, which was either classified as low-demand

(focusing on two geometric objects), or as high-demand (focusing on four geometric objects). Tests were further

categorized as non-distractor (no outside interfering stimuli), otherwise known as the A condition, or as distractor (non-

target stimuli were present), called the S condition. In the A condition, participants were asked to identify the location of

all of the shapes (circles and squares) on the grid, whereas in the S (distractor) condition, they were asked to focus only on

the locations of the squares. The participants would be shown the image for two seconds, and then the shapes would

disappear. A cross-figure would appear in a spot on the grid six seconds later, and the participant would have to classify it

as either match (the cross is in the same spot as a target geometric figure) or nonmatch (the cross is not in the same spot as

the geometric figure). Half of the trials were designed as match trials (the cross would appear in the former location of a

geometric figure), and the other half were designed as nonmatch trials (the cross would appear in a location never

inhabited by a geometric figure). The participant would then have to rate how confident they were in their answers, with

A corresponding to confident and S corresponding to not confident. They were given as much time as they needed to

accurately respond to this portion of the test.

Mayer and Park (2012) then analyzed response accuracy, response time (RT), and the different types of responses,

which included true memory responses, correct but not-confident responses, false memory responses, and incorrect and

not-confident responses. The primary focus was placed on the nonmatch 4 item no-distractor trials because the cross

appeared adjacent to the target locations with a greater rate than in the other conditions of the test. The absence of

distractors also made it easier, in theory, for the participants to tend to the correct stimuli, thus reducing the odds of

encoding errors due to faulty attentional capture. The types of probes used to elicit answers were classified as either near

to target or far from target, as the researchers hypothesized that more false memory errors would occur when the

participants were presented with probes from the former category – such stimuli could be easily mistaken as accurate due

to their close proximity to the actual target. In both load two and four tasks without distractors, schizophrenics scored

both the lowest percentage of accurate responses and the highest reaction time to produce their answers. Schizophrenic

patients reported greater confidence in their answers than all other groups, and were more likely to report seeing a


geometric shape in probes that were closer to the target than further from the target. The similar locations added to their

confidence that they were answering accurately.

Because the test was structured to incapacitate the enhancement of encoding by allowing little time for rehearsal,

it seems likely that errors with false memory occur as early on as encoding. When given a greater amount of time to

perform the same task (hence, having a better chance of accurately encoding information), the control population had

more accurate and more confident responses, while the schizophrenic population performed no differently compared to

tasks in which they had significantly less time to rehearse information. Also, RT and false memory did not show a

positive correlation, so it is unlikely that schizophrenic persons experienced errors in information retrieval; if the retrieval

stage was faulty, then reaction time would be expected to increase due to the complexity of recalling information. The

amount of false memory errors was not shown to correlate with the severity of the disease in this study, as all the

schizophrenic participants scored within the same relative range. It is interesting to note, however, that relatives of

schizophrenics who were not suffering the disease themselves scored less accuracy and had lower RTs than the healthy

controls, so it is likely that there is a biological component to encoding and recognition errors that lead to false memory.

Allen et al. (2009) studied such biological components by combining a DRM task with fMRI scans. The DRM

task presented the participants (18 at-risk mental state persons in the beginning stages of schizophrenia and 22 healthy

controls) with lists of words which they would have to recall after a twelve-minute delay, during which the participants

were given an attention task unrelated to the word list so that the encoding process would be strained. During the actual

encoding phase of the task, participants would have to read the word list aloud; after the aforementioned twelve minute

delay, the participants were presented with 24 target words, 24 semantically-related lure words, and 24 novel words.

They would then have to confirm whether or not they had been presented with these words before. The at-risk group had

a greater rate of false alarms (new words that were reported as old words with a high level of confidence) than the control

group for the novel words and were less able to accurately differentiate the actual target words. The results were highly

similar to Mayer and Park’s study in terms of false memory linked probe/target testing (for example, the word “bog”

could easily be confused with the word “bag,” whereas the words “bog” and “lag” were less similar and thus less likely to

be confused for one another), which shows a common pattern comparing schizophrenics to the control population. The

fMRI results, however, presented interesting findings. During the encoding period, the hippocampal region of

schizophrenic participants was lower than that of healthy controls. The same region was also overactive compared to the


controls during periods of false memory, which indicates that the hippocampus is relevant to both processes. As the

hippocampus is involved in memory tasks, it seems that schizophrenics indeed err during the encoding phase and attempt

to compensate at later phases, although the results are inaccurate. Schizophrenics also showed less activity in their left

and medial prefrontal regions, which are both involved in executive functioning. These underactive regions map out the

lack of executive functional performance in schizophrenics, which is one of the contributors to their inability to carry out

daily tasks.

Caza et al. (2011) also utilized the DRM to test false memory in schizophrenic patients. The sample size was 17

schizophrenic adolescents and 17 healthy controls matched to the experimental group; the researchers felt that it was

especially important to study persons who had not yet been exposed to long-term treatment of both medical and

institutional varieties. This would eliminate some of the possible differences in terms of symptoms in the sample size and

provide a more accurate representation of the schizophrenics’ baseline abilities sans external intervention. Overall, true

memory (accurate response with high confidence) was impaired in the patients as compared to the control group. While

false memory was equal across both groups when presented with a critical lure, false memory was increased in patients

when they were presented with an unrelated distractor, which inhibits the encoding process. Patients were able to report

fewer words and made more intrusions, both related and unrelated, than the healthy controls. RTs for the schizophrenic

group were also lower than the control group’s reaction times, signifying that the issue was not that of recollection. The

researchers believe that the encoding errors are due to the schizophrenic’s inability to accurately utilize verbatim

memorization (what exactly was said) and are thus forced to rely on gist memorization (what the words meant in general,

not specifically). This type of memory makes room for more error, as things which are similar are easier to misconstrue

than things which are retained with accuracy. Such trends lead to false memory, as the patients remain confident in their

gist memories and oblivious to their complete lack of verbatim traces.

Finally, Bhatt et al. (2010) measured whether or not there is an increased amount of false memory in

schizophrenics currently experiencing delusions (ED) when compared to those not experiencing delusions (ND) and

healthy controls. This study also utilized the DRM test with consistent results as the above study – low recall rates for

both schizophrenic groups compared to the control group, greater intrusions by both groups of schizophrenics, and higher

confidence in schizophrenics than the control group. The ED group, however, made more false memory errors than the

ND group, which may suggest that delusions (perhaps due to an overactive hippocampus in false memory states according


to Allen et al.’s study) correlate to a lesser level of encoding. Because the delusions are most likely highly distracting for

the ED person, they do not focus as well on the information they are presented with. Paranoid schizophrenics were also

shown in this study to be more susceptible to false memory, as they are more likely to trust the information in

lures/distractors. As paranoid schizophrenics are among the most heavily delusional, it can be reaffirmed that delusions

do, in fact, lead to higher false memory errors.

But why does any of this matter? First and foremost, the components of schizophrenia must be understood before

the disease can ever be sufficiently treated. As false memory can be particularly dangerous (imagine the legal issues a

person could get into, whether they are perpetrating a crime in unnecessary “self-defense” or accusing an innocent person

of a crime) it is urgent to resolve such issues sooner rather than later. False memory also leads to a lower-quality life, as

schizophrenic patients are less able to lead healthy lives than the average person, often ending up financially dependent or

homeless. Studying recall and encoding tasks is also beneficial to the wider population, as it teaches us how we all handle

information. Such data could be used to further study learning processes and disabilities of all kinds, with focus on

schizophrenia being but one route that could be studied. Also, false memory can undermine close social relationships

because it sometimes causes extreme mistrust and paranoia. A person who wishes to bond with a schizophrenic may have

their actions misinterpreted (encoding a friendly smile as a threatening gesture and later having false memories of a

confrontation that never occurred) and may be met with hostility in return. It is necessary to analyze faulty encoding

because strategies that attempt to correct this process could be implemented by therapists and drastically increase the

quality of life for schizophrenic individuals.

In conclusion, false memory is higher in schizophrenic persons than in the average population, and is caused

primarily by errors within the encoding phase. Mayer and Park (2012) found that schizophrenic patients had lower RTs

and greater confidence while reporting their answers on the spatial DRT task. Even when given a greater amount of time

to rehearse information (and thus encode it), schizophrenics performed the same, whereas the control group performed

significantly better. False memory is also more likely when the location of the nonmatch stimulus is spatially closer to the

target, which seems to point towards less specific attention utilized during encoding. Allen et al. (2009) found that the

hippocampal region, which is a major player in information encoding, is underactive in schizophrenic patients during the

DRM task, which is also focused around encoding abilities. Thus the encoding process itself is likely corrupted – a brain

region is less active when it should be highly involved. Caza et al. (2011) also utilized the DRM task and gathered the


same pattern of results – schizophrenics have lower RTs than controls but also have higher occurrences of false memory.

This seems to be due to the schizophrenics’ inability to encode verbatim information – which is highly accurate – and

instead are forced to rely on gist-oriented information, which can easily be distorted. The information, therefore, was not

entirely correct from the very beginning – the encoding phase. Lastly, Bhatt et al. (2010) examined the difference in

encoding ability between schizophrenics experiencing delusions and not experiencing delusions. The ED group had a

greater level of false memory responses when compared to the NED group. The distraction of these delusions is likely

inhibitive to the encoding process, because it makes the new information more difficult to focus on and accurately take in.

Encoding is already impaired in schizophrenics, and any additional distractor will further hinder the process, and lead to

greater instances of false memory.


Works Cited

Allen, P., Valli, I., Fusar-Poli, P., Perlini, C., Day, F., McGuire, P.K., Seal, M.L., Wood, S.J., and Williams,

S.C. (2011). Altered prefrontal and hippocampal function during verbal encoding and recognition in

people with prodromal symptoms of psychosis. Schizophrenia Bulletin, 37(4), 746-756.

Bhatt, R., Laws, K.R., and McKenna, P.J. (2010). False memory in schizophrenia patients with

and without delusions. Psychiatry Research, 178(2), 260-265.

Caza, Nicole, Dore, Marie-Claire, Gingras, Nathalie, and Rouleau, Nancie. (2011). True and false memories in

adolescents with psychosis: Evidence for impaired recollection and familiarity. Cognitive

Neuropsychiatry, 16(3), 218-240.

Mayer, Jutta S., and Park, Sohee. (2012). Working memory encoding and false memory in schizophrenia and

bipolar disorder in a spatial delayed response task. Journal of Abnormal Psychology, 121(3), 784-794.

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Schizophrenia and working memory