Abstract
Constructivists about memory argue that memory is a capacity for building representations of past events from a generalized information store (e.g., De Brigard, in Synthese 191:155–185, 2014a; Michaelian, in Philos Psychol 24:323–342, 2012). The view is motivated by the memory errors discovered in cognitive psychology. Little has been known about the neural mechanisms by which false memories are produced. Recently, using a method I call the Optogenetic False Memory Technique (O-FaMe), neuroscientists have created false memories in mice (e.g., Ramirez et al., in Science 341:388–391, 2013). In this paper, I examine how Constructivism fares in light of O-FaMe results. My aims are two-fold. First, I argue that errors found in O-FaMe and cognitive psychology are similar behaviorally. Second, Constructivists should be able to explain the former since they purport to explain the latter, but they cannot. I conclude that O-FaMe studies reveal details about the mechanism by which false memories are produced that are incompatible with the explanatory approach to false memories favored by Constructivism.
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Notes
I resist labeling these memories of particular past events as episodic so as to avoid debates over whether episodic memory must involve a rich phenomenal character and whether non-human animals are capable of episodic remembering. I prefer the more neutral category event memory, for reasons elaborated on in Sect. 4.1.
The genealogy of non-human animal models of false memory extends back further, of course. I discuss the recent history of this research in Sect. 3.
Gallo (2006) offers a thorough review of the DRM and its various permutations.
It is worth noting that these results reflect performance tendencies across large groups of participants. Not everyone who engages in such tasks produces false memories, nor does everyone produce the same rates of error or fall prone to the same manipulations. Thanks to an anonymous reviewer for pressing this point.
This does not mean that all experimentalists who conduct studies of these memory errors endorse Constructivism, although of course some do (e.g., Loftus 2003). My focus is on contemporary philosophical versions of Constructivism, which take such evidence as motivation for their views.
There are many variants of Constructivism; where individual accounts disagree, my exposition below follows the commitments of De Brigard.
Versions of Constructivism can be distinguished by the specific distributed architecture endorsed. For a discussion of these variations, see Robins (forthcoming).
The claim that memory responds accurately most of the time may strike the reader as difficult to reconcile with De Brigard’s other claim, quoted in Sect. 2.1, that memory “regularly and systematically malfunctions” (2014a, p. 159). Proponents of Constructivism must maintain a fine balance here, between claiming that memory follows certain patterns that are generally reliable and that the possibilities for error are pervasive enough to motivate this alternative account of memory. This is an interesting tension in the view, and I am grateful to an anonymous reviewer for highlighting it, but I do not explore it further in this paper.
For the purposes of this paper, the terms “engram” and “memory trace” are being used interchangeably.
It is an interesting to ask whether, in the neuroscience of memory, commitment to the existence of discrete memory traces is a pretheoretical commitment or empirical discovery. For a discussion of this issue, see De Brigard (2014b).
Although, of course, philosophers of neuroscience disagree about the explanatory lessons to be drawn from consideration of this example. Bickle (2003) uses memory formation as an example of “ruthless” reduction, whereas Craver (2007) advocates multi-level mechanisms. For concerns about the explananda, see Sullivan (2010).
Freezing is an adaptive response to fear, as predators are often sensitive to motion, and is found in most rodents.
For a thorough review of optogenetic techniques, see Deisseroth (2011).
This is not to say that the method is without its limitations (Häusser 2014). Some even recommend more focus on alternative molecular interventions, such as designer receptors exclusively activated by designer drugs (DREADDs), and the relative experimental advantages and disadvantages of each (Bickle forthcoming).
The transgenic population used by the Tonegawa laboratory for the O-FaMe studies discussed below are c-fos/tTA/Dox-off mice. In addition to the features discussed in the text, these mice are also engineered to have: (1) A tetracycline-responsive element (TRE), which provides a binding site for the protein that allows expression of the engineered opsin gene), and (2) Monomeric fluorescent protein gene (mCherry), which expresses a protein that appears red under standard light microscopy, allowing the engram cells to be detected by researchers. Many thanks to John Bickle for helping me understand the details of this mechanism.
The lineage of O-FaMe, and inquiries into the possibility of animal models of false memory, can be traced back further, to studies that manipulate which neurons are involved in the engram by interventions into the CREB transcription factor (Han et al. 2007).
Another portion of the Redondo et al. study involved a comparison of encoding-related changes in the amygdala versus the dentate gyrus. This portion of the results confirms that it is the neural changes in the dentate gyrus, not the amygdala, that are responsible for engram formation.
The rates of false recognition were lower, however. Only 25 % of participants “recognized” the photo without the misleading question on the questionnaire, whereas 60 % “recognized” it when the misleading question was included.
I am grateful to Jacqueline Sullivan for raising this issue.
To make this point more forcefully, O-FaMe studies should include a fourth condition, where the mouse is taken to a familiar, neutral context. If the mouse treats the environment as familiar, but does not freeze, then it would be clear that the misinformation has not spread to all remembered contexts. To my knowledge, no O-FaMe study has yet included such a condition.
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Acknowledgments
Many thanks to audiences at the University of Colorado’s 2014 HPS Conference, the Southern Society for Philosophy and Psychology meeting in New Orleans, and the Society for Philosophy and Psychology meeting at Duke University. I am especially grateful to John Bickle, Paul Davies, Corey Maley, Joseph McCaffrey, and Jacqueline Sullivan, as well as two anonymous reviewers, for their detailed and thoughtful feedback. Completion of this manuscript was supported by the University of Kansas General Research Fund allocation #2301035.
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Robins, S.K. Optogenetics and the mechanism of false memory. Synthese 193, 1561–1583 (2016). https://doi.org/10.1007/s11229-016-1045-9
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DOI: https://doi.org/10.1007/s11229-016-1045-9