Ink Of Dreams Research Papers

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There I stood, at the recent Society for Information Display (SID) 2001 International Symposium, Seminar and Exhibition, surrounded by the coolest collection of display technologies in the world — next-generation LCDs with brilliant color, plasma screens big enough to cover a wall of my apartment, other displays smaller than a thumbnail — and my favorite demonstration was the display with questionable resolution, no color, and an unusual form factor. It was labeled “electronic paper,” and it looked like its namesake — a thick piece of paper with crisp black ink on a white background that nonetheless holds a computer-generated, impermanent image.

Now the idea of something called electronic paper or electronic ink (the terms are used interchangeably) being part of display show may seem odd. “Display” brings to mind bulky CRTs and flat-panel LCDs. But this super-slim, portable viewing screen was right at home at SID, which was held earlier this month in San Jose, California. The future was literally on display at the show, or rather, many possible futures for displays, depending on the booth and the volume of its marketing pitch. SID is a place for industry insiders (anyone making his or her way into the hall automatically becomes a member of the club) to get a good look at forthcoming OEM screen components as well as prototypes that are two or three generations out. I spied hardware bigwigs from Apple and other system vendors in attendance. Some of these designs and technologies may (or may not) make their way into mass production.

But after looking intently at all those gorgeous LCD displays I was intrigued by the possibilities of electronic ink. This minimalist display could shortly become an important content distribution platform.

The E-ink Spots
I had read articles about electronic ink or paper, but seeing it in action brought me close to becoming a believer. The technology demonstrated at SID was from a company called E Ink Corp., based in Cambridge, Mass. (MIT’s Media Center and of course Xerox’s Palo Alto Research Center have proposed similar schemes.) The “display” in this case is a rectangle of film that looks much like a piece of paper — thin and flexible, with black text and images on a white background (although they also showed grayscale and color versions).

Unlike traditional displays in which a constant light source brings the image to life, electronic ink allows viewing independent of a steady power supply or even a computing device. When you turn off the electronic paper, magic happens: The image remains on the screen. The upshot is that you can carry an e-ink display with you all day long, checking its image or text, without needing a constant stream of power. Only when you need to change what’s displayed do you need to access your computer and use some power.

The film that makes up E Ink’s electronic paper consists of millions of microcapsules, each containing a soup of opaque white and black particles suspended in a clear liquid. When different electric fields are applied to the film, one flavor of the particles moves to the top of the microcapsule. So, if the white moves to the top, it hides the black goop underneath. More importantly, each microcapsule retains its setting even when the power stops. It’s the opposite of the usual flat-panel displays and CRTs that we’ve grown up with, where no power means no image.

To my amazement, I found the resulting e-ink image to be sharp and glare-free (depending on the application, the e-ink media might be covered by plastic or some other coating that could cause reflections).

While the film can be bonded to a variety of surfaces, it can also be placed directly on a plastic substrate that contains the display circuitry. According to C. Howie Honeyman, E Ink chief scientist, the company’s display is flexible but can’t be folded. Yet, it’s possible to easily drill a hole in the material, for example, letting one place the sheets in a standard three-hole binder, if one was in a particularly retro mood.

Moveable Media
The uses for electronic ink are many. At SID, Philips said it will use electronic ink for a PDA display next year. It’s also a natural for point-of-purchase signage.

The advantage of e-ink for a PDA is obvious — battery life can be extended dramatically, since the screen only needs power when it changes the data on the screen. Compare that to my usual annoying PDA experience: In its ongoing quest to save battery life, my Palm Pilot always seems to turn itself off right when I’m dialing a phone number. With e-ink, the record will stay on the screen until I want to look for another record or switch applications. It doesn’t need to keep tapping the power supply to remain visible.

In addition, e-ink could spark a new digital book or magazine market. Imagine a lightweight, inexpensive read-only device incorporating wireless technology, a limited processor and battery, and a two-page, letter-size display. Thinner than a binder, the device would provide much of the experience of today’s magazines, but with a hardcover. With its easy manufacturing, the e-magazine cost could be similar to a hard-bound book, well under $50. Figure 1 shows a recent prototype from Philips, but I’d like a larger, magazine-style spread.

Today, e-books or similar content are usually demonstrated on PDAs or notebook computers. With their pint-size screens, PDAs offer a sub-par reading experience. Laptop screens provide a great image, but their size makes for poor battery life. And laptops are cumbersome and difficult to hold.

Moreover, both PDAs and laptops are designed to be general-purpose computing platforms, supporting interactivity, Internet access, and even multimedia. The cost of these features may be essential for a computer, but they are arguably overkill for a content-reading device. The loss of a paperback or hardbound book will bring disappointment and regret, but it’s usually replaceable. With mass-production, an e-ink book might carry a similar cost. On the other hand, it’s panic time if you leave your laptop in a taxi. And it has all your personal data!

The purchase of an e-ink reading device could also be separated from content. Users could purchase a reader with built-in content, just as they do with today’s content delivery model, or instead they could subscribe to wireless content services. The company would track the items we’ve read as well as deliver on demand new material or updates.

If you leave your reader at home (or on the subway), you simply walk to a newsstand or bookstore, purchase a new empty book, feed it your account number, and then wait for the package of content to be transferred to the e-ink device. In a controlled environment such as school, students could receive the news and coursework for the week.

The current lack of a compelling hardware platform must cause grief for advocates of e-books. They are hard-pressed to answer the tough question from potential buyers: Will I be able to take my e-book to the beach or into the bathroom? The forthcoming E-ink devices, with their low cost, convenience, and familiar user experience, may offer the answer.

Back to the Future
Inevitably, there will be production and design challenges for content creators when authoring to any future e-ink platform. Some of the trouble may come from designing for monochrome screens, something that we now consider a relic of the past. We’ve repressed the memories of a time when monochrome monitors were the norm. Today, outside of print, most designers assume that high-resolution color will be available for their images and layouts.

While prototypes are notoriously fickle, I found that E Ink’s black-and-white model performed the best; its grayscale version showed ghosting when refreshing images, and the color model was demonstrated with a static test pattern. Even when the technology improves, the lowest cost product (and the likely winner in the market) may be found with just two colors, black and white.

So, content creators aiming to repurpose images will need to consider how their color designs will play in print as well as in monochrome on an e-ink page.

One SID attendee found the e-ink images “nostalgic,” reminding him fondly of Bill Atkinson’s ground-breaking HyperCard information authoring utility for the Macintosh. “The [e-ink] page was appealing because it was monochromatic and dithered,” explained Joel Ingulsrud, a former display product manager at SGI.

Whether or not content creators appreciate e-ink’s eventual performance, its potential is huge. Of course, that’s all it is right now, even after my imagining of an entire new market. The Talmud informs us: “Many pens are broken and seas of ink consumed, to describe things that never happened.” Still, I think electronic ink is a technology to watch, one with a real chance to make it.

Categories: Features, Print, Print Design & Layout, Web/Mobile


The level and nature of our conscious experience varies dramatically in sleep. During slow wave sleep (SWS) early in the night, consciousness can nearly vanish despite persistent neural activity in the thalamocortical system[10]. Subjects awakened from other phases of sleep, especially but not exclusively during REM sleep, report “typical”, full-fledged dreams - vivid, sensorimotor hallucinatory experiences that follow a narrative structure[3, 11]. The dreamer is highly conscious (she has vivid experiences), is disconnected from the environment (she is asleep), but somehow her brain is creating a story, filling it with actors and scenarios, and generating hallucinatory images. How does the brain accomplish this remarkable feat? And, conversely, what do dreams tell us about the organization and working of the brain?

Since awakenings from REM sleep regularly yield reports of typical dreams, we will first focus on neural activity during REM sleep, to gain insight into brain states that are compatible with dreaming. It should be emphasized at the outset, however, that dreams can occur in other brain states, such as late NREM sleep, as will be discussed below.

Similarities between dreaming and waking

In order to gain insight into the phenomenology and neural basis of dreams, it is useful to consider both similarities and differences between waking consciousness and dreaming consciousness, and to relate these differences to changes in brain activity and organization[11]. Perhaps the most striking feature of conscious experiences in sleep is how altogether similar the inner world of dreams is to the real world of wakefulness. Indeed, at times the dreamer may be uncertain whether he is awake or asleep. Certainly, dreams are not created in a vacuum but closely reflect the organization and functions of our brain.

In most dreams, perceptual modalities and submodalities that dominate in wakefulness are heavily represented. Dreams are highly visual, in full color, rich in shapes, full of movement, and incorporate typical wakefulness categories such as people, faces, places, objects, and animals[3]. Dreams also contain sounds (including speech and conversation), and more rarely tactile percepts, smells and tastes, as well as pleasure and pain[4, 12–14]. Experiences in typical dreams have a clear sensory character (i.e. they are seen, heard, and felt) and are not mere thoughts or abstractions.

These phenomenological similarities are reflected in neurophysiological similarities between waking and dreaming. For historical and methodological reasons, most electroencephalogram (EEG) and neuroimaging studies have contrasted brain activity during quiet wakefulness with that observed during REM sleep, when subjects are most likely to report dreams[15–20]. At least superficially, the EEG looks remarkably similar in active waking and REM sleep. Positron emission tomography (PET) studies have shown that global brain metabolism is comparable between wakefulness and REM sleep[11, 20]. Such studies have also revealed a strong activation of high-order occipito-temporal visual cortex in REM sleep, consistent with the vivid visual imagery during dreams (Fig. 1)[16, 17, 19].

There is also remarkable consistency between a subject s cognitive and neural organization in dreaming and waking[13, 14]. For instance, children studies demonstrate that dream features show a gradual development that parallels their cognitive development when awake[21] (Box 2). Patients with brain lesions that impair their waking cognition show corresponding deficits in dreams. For example, subjects with impaired face perception also do not dream of faces[22, 23] (Box 3).

BOX 2The development of dreams in children

When do children start dreaming, and what kind of dreams do they have? Since children often show signs of emotion in sleep, many assume they dream a great deal. However, a series of studies by David Foulkes showed that children under the age of 7 reported dreaming only 20% of the time when awakened from REM sleep, compared with 80–90% in adults[21].

Preschoolers dreams are often static and plain, such as seeing an animal or thinking about eating. There are no characters that move, no social interactions, very little feeling, and they do not include the dreamer as an active character. There are also no autobiographic, episodic memories, perhaps because children have trouble with conscious episodic recollection in general, as suggested by the phenomenon of infantile amnesia. Preschoolers do not report fear in dreams, and there are few aggressions, misfortunes, and negative emotions. Note that children who have night terrors, in which they awaken early in the night from SWS and display intense fear and agitation, are probably terrorized by disorientation due to incomplete awakening rather than by a dream[116]. Thus, although children of age 2–5 can obviously see and speak of everyday people, objects and events, apparently they cannot dream of them.

Between ages 5 to 7 dream reports become longer, although still infrequent. Dreams may contain sequences of events in which characters move about and interact, but narratives are not well developed. At around age 7, dream reports become longer and more frequent, contain thoughts and feelings, the child s self becomes an actual participant in the dream, and dreams begin to acquire a narrative structure and to reflect autobiographic, episodic memories.

It could be argued that perhaps all children dream, but some do not yet realize that they are dreaming, do not remember their dreams, or cannot report them because of poor verbal skills. Contrary to these intuitive suggestions, dream recall was found to correlate best with abilities of mental imagery rather than language proficiency. Mental imagery in children is assessed by the Block Design Test of the Wechsler intelligence test battery[117]. In this task, children look at models or pictures of red and white patterns, and then recreate those patterns with blocks. Critically, scores on this test are the one parameter that correlates best with dream report in children. Put simply, it is children with the most developed mental imagery and visuo-spatial skills (rather than verbal or memory capabilities) that report the most dreams, suggesting a real difference in dream experience. Visuo-spatial skills are known to depend on the parietal lobes, which are not fully myelinated until age 7. Thus, linking visuo-spatial cognitive development with brain maturation studies[118] is an important field of further research.

The static nature of preschoolers dreams is also in accord with the notion that preoperational children can’t imagine continuous visual transformations[119]. In the “mental rotation” test[120] a subject is asked to determine whether two figures are the same or different. In adults, reaction times (which are used as the score) increase linearly with the degree of rotation, but children do not show this relationship and do not seem to be mentally imagining movement using visuo-spatial imagery. This is consistent with their dream reports lacking movement[21].

Along the same line, people who are blinded after the age of 5–7 seem to have visual imagination and dream with visual imagery throughout life, while blinding at an earlier age leads to absence of visualization in both waking and dreaming[121, 122], though dreaming in blind individuals is a subject of debate[123–125]. Overall, dreaming appears to be a gradual cognitive development that is tightly linked to the development of visual imagination.

The slow development of full-fledged dreams and their intimate relation with imagination cast doubts on whether animals can dream as we do. It is likely that animals, too, can be conscious during sleep. For instance, lesions in parts of the brainstem that control movements cause cats to seemingly act out their dreams[126], very much like humans with REM sleep behavior disorder [113]. However, while a cat may experience images and emotions in sleep, it is less likely that these experiences are tied together by a narrative as is the case in our typical dreams[127]. Altogether, what kind of dreaming consciousness an animal has may reflect the extent to which it is conscious in general, and both waking and dreaming consciousness are best viewed as graded phenomena[80].

BOX 3Lesion studies of dreaming

The primary source on neuropsychology of dreaming is a study by Solms[22] who examined 361 neurological patients and asked them in detail about their dreaming. Overall, lesion studies indicate that dreaming depends on specific forebrain regions rather than on the brainstem REM sleep generator[22, 128, 129]. In most cases, global cessation of dreaming follows damage in or near the temporo-parieto-occipital junction (around Brodmann’s Area 40), more often unilaterally than bilaterally[23, 128]. This region supports various cognitive processes that are essential for mental imagery[130]. Accordingly, patients with such damage typically show a parallel decline in waking visuo-spatial abilities[109]. These results strongly suggest that mental imagery is the cognitive ability most related to dreaming (though a link between loss of dreaming and aphasia has also been suggested[131]).

Less frequently, global cessation of dreaming follows bilateral lesions of white matter tracts surrounding the frontal horns of the lateral ventricles, underlying ventromedial prefrontal cortex[22]. Many of these nerve fibers originate or terminate in limbic areas, in line with increased limbic activity in REM sleep as revealed by functional imaging[15, 16, 18]. The ventromedial white matter contains dopaminergic projections to the frontal lobe which were severed in prefrontal leucotomy, once performed on many schizophrenic patients[53]. Most leucotomized patients (70–90%) complained of global cessation of dreaming as well as of lack in initiative, curiosity, and fantasy in waking life[23]. Since dopamine can instigate goal-seeking behavior, these data have been interpreted as supporting the classical psychodynamic view of dreams as fulfillment of unconscious wishes related to egoistic impulses[132].

Apart from global cessation of dreaming, more restricted lesions produce the cessation of visual dreaming [22, 109], or the disruption of particular visual dimensions in dreams. For example, lesions in specific regions that underlie visual perception of color or motion are associated with corresponding deficits in dreaming[23, 109]. In general, it seems that lesions leading to impairments in waking have parallel deficits in dreaming.

Some lesions, especially those in medial prefrontal cortex, the anterior cingulate cortex, and the basal forebrain, are associated with increased frequency and vividness of dreams and their intrusion into waking life[22]. Importantly, many brain-damaged patients report no changes in dreaming, indicating that the neural network supporting dreaming has considerable specificity. For example, lesions of dorsolateral prefrontal cortex, sensorimotor cortex, and V1 do not seem to affect dreaming at all[22]. The fact that patients with V1 lesions report vivid dreaming argues against the notion that reentry to early retinotopic cortex is a necessary condition for visual awareness[133].

Dreams also reflect our interests and personality, just like mental activity during wakefulness. Formal content analysis has revealed that mood, imaginativeness, individuals of interest, and predominant concerns are correlated between our waking and dreaming selves[12–14]. Personal anxieties we experience in wake, such as being inappropriately dressed, being lost, or being late for an examination, can appear in dreams that involve social interactions[24]. Dreams, like our personality in general, are quite stable over time in adulthood[12–14], and share many characteristics across cultures[12–14]. In addition, we feel we are personally participating in many dream events.

Despite these remarkable similarities, what makes dream consciousness so fascinating are the ways in which it differs from our waking experience. Some of these phenomenological differences are accompanied by consistent neurophysiological differences.

Reduced voluntary control and volition

We are generally surprised on awakening from a dream (“it was only a dream”) mainly because we didn’t consciously will that we would dream it. In fact, during dreaming there is a prominent reduction of voluntary control of action and thought. We cannot pursue goals, and have no control over the dream’s content. The fact that we are so surprised, excited and even skeptical about lucid dreaming – possibly a way to control some dreams[25] - illustrates how dreams normally lack voluntary control[9]. Interestingly, recent evidence points to the role of the right inferior parietal cortex (Brodmann’s Area 40) in waking volition[26, 27], an area that is deactivated during REM sleep[15, 16] (Fig. 1).

Reduced self-awareness and altered reflective thought

Our dreaming consciousness consists of a single “track”: we are not contextually aware of where we are (in bed) or of what we are doing (sleeping, dreaming). There is a strong tendency for a distinct narrative of thoughts and images to persist without disruption (“single-mindedness”[28]). Indeed, reports of mental activity in REM sleep are longer than reports obtained from awake subjects[28]. Dreaming is almost always delusional since events and characters are taken for real. Reflective thought is altered in that holding contradictory beliefs is common, and a dreamer easily accepts impossible events such as flying, inconsistent scene switches, sudden transformations and impossible objects[29] such as a pink elephant. There is often uncertainty about space, time, and personal identities[30]. For example, a character may have the name, clothes and hairstyle of a male friend, but have mother’s face. Reduced self-monitoring in dreams may be related to the deactivation of brain regions such as posterior cingulate cortex, inferior parietal cortex, orbitofrontal cortex, and dorsolateral prefrontal cortex[15, 16] (Fig 1). Indeed, deactivation of prefrontal cortex has been shown to accompany reduced self-awareness during highly engaging sensory perception in wakefulness[31]. However, some dreams may have conserved reflective thought processes such as thoughtful puzzlement about impossible events[32], contemplating alternatives in decision-making[32], reflecting during social interactions[32], and “theory of mind”[33], demonstrating that individual dreams can differ from each other substantially.


Some dreams are characterized by a high degree of emotional involvement, including joy, surprise, anger, fear, and anxiety[34–36]. Interestingly, sadness, guilt, and depressed affect are rare[11], possibly due to reduced self-reflection. Some claim that fear and anxiety are enhanced in dreams to a degree rare in waking life[37], in line with Freud’s suggestion that dream narratives originate in perceived threats or conflicts[5]. Whether or not this interpretation has merits, REM sleep is in fact associated with a marked activation of limbic and paralimbic structures such as the amygdala, the anterior cingulate cortex, and the insula[15, 17, 19] (Fig. 1). However, emotions are feeble in other dreams, and are absent altogether in 25–30% of REM sleep reports[34–36], including in situations where emotions would likely be present in waking[34], once again highlighting the variability in dream phenomenology.

Altered mnemonic processes

Memory is drastically altered for the dream and within the dream. Unless the dreamer wakes up, most dreams are forever lost. Upon awakening, memory for the dream often vanishes rapidly unless written down or recorded, even for intense emotional dreams. It is not clear why this is the case since from a neuroimaging perspective, limbic circuits in the medial temporal lobe that are implicated in memory processes, are highly active during REM sleep[15–18] (Fig. 1). Perhaps the hypoactivity of prefrontal cortex, also implicated in mnemonic processes, plays an important role in dream amnesia. Contemporary theories of dreaming (Table 1) offer different accounts of dream amnesia. For example, according to psychodynamic models, dream amnesia is due to processes of active repression[5]. According to Hobson s Activation-Input-Mode [AIM] model, dream amnesia is related to a state-change involving inactivity of monoaminergic systems (“aminergic de-modulation”) and deactivation of dorsolateral prefrontal cortex[11]. The neurocognitive model claims that dreams are usually forgotten because they are internal narratives; unless internal experiences are tied to external cues such as times and places they are bound to be forgotten[13].

Table 1

Contemporary theories of dreaming

Episodic memory is also impaired within the dream. Indeed, a dream is not like an episode of life being “replayed”. In one example in which subjects had intensively played the computer game Tetris, there was no episodic memory in subsequent dreams that subjects had indeed played Tetris. In fact, dreams of healthy subjects were indistinguishable from those of profoundly amnesic subjects, who could not remember having played Tetris at all. In contrast, both normal and amnesic subjects often reported perceptual fragments, such as falling blocks on a computer screen, at sleep onset[38]. While ‘residues’ from waking experience are incorporated in about 50% of dreams[39–41], they do so in new and unrelated contexts, and verified memories for episodes of recent life are only found in about 1.5% of dreams[42]. Such residual recollections have been interpreted by some to suggest that dreaming may have an active role in forgetting[5, 43]. Finally, many have the impression that the network of associations stored in our memory may become looser than in wake[44, 45], perhaps favoring creativity, divergent thinking, and problem resolution[4, 46].

In summary, dream consciousness is remarkably similar to waking consciousness, though there are several intriguing differences. These include reduced attention and voluntary control, lack in self-awareness, altered reflective thought, occasional hyperemotionality, and impaired memory. Traditionally, dream phenomenology has often been compared to madness or psychosis[3, 11, 47], but in fact the hallucinations, disorientation, and subsequent amnesia of some bizarre dreams may be more akin to the acute confusional state – also known as delirium - which occurs after withdrawal from alcohol and drugs[48]. However, most dreams are less bizarre, perhaps more similar to mind wandering or stimulus independent thoughts[14, 49, 50]. Waking thoughts jump around and drift into bizarre daydreaming, rumination, and worrying far more than stereotypes of rational linear thinking suggest[51]. Importantly, individual dreams are highly variable in their phenomenology, and only some conform to the typical monolithic template that is often portrayed. Thus, just like diverse waking experiences, “Not all dreams are created equal”, and future studies should consider different kinds of dreams and their neural correlates separately.

What mechanisms are responsible for regional differences in brain activity between waking and REM sleep, and thus presumably for some of the cognitive differences between waking and dreaming? Single-unit physiology indicates that generally, cortical activity in REM sleep reaches similar levels as found in active wake (Fig. 2), but variability between brain areas remains poorly explored. Regional differences may likely stem from changes in the activity of neuromodulatory systems (Fig. 2). During REM sleep, acetylcholine is alone in maintaining brain activation, whereas monoaminergic systems are silent, an observation that could explain many features of dreams[11]. For example, consistent with imaging results, cholinergic innervation is stronger in limbic and paralimbic areas than in dorsolateral prefrontal cortex[52], which may explain why limbic regions are highly active in REM sleep while dorsolateral prefrontal cortex is deactivated (Fig. 1). Dopaminergic modulation may also play a role[23], since dreaming is decreased by prefrontal leucotomies that cut dopaminergic fibers[53] and is increased by dopaminergic agonists[23] (Table 1 and Fig. 2).

Figure 2

Neurophysiology of wake and sleep states

On the whole, relating typical dreams to the neurophysiology of REM sleep has proven to be a useful starting point for revealing the neural basis of dreaming. However, dream consciousness can not be reduced to brain activity in REM sleep. Indeed, some fundamental questions concerning the relationship between the brain and dreaming linger on. We shall discuss three in turn: i) what determines the level of consciousness during sleep; ii) why the dreamer is disconnected from the environment; and iii) whether dreams are more akin to perception or to imagination.

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