Saturday, February 27, 2010

Justice Department Launches Investigation of JRC

Good news from Left Brain/Right Brain: In response to a letter of complaint written by disability advocate Nancy Weiss, who is co-director of the National Leadership Consortium on Developmental Disabilities and an Assistant Professor of Human Development and Family Studies at the University of Delaware, and signed by thirty-one disability organizations (including Weiss's organization, the NLCDD, TASH, the Autistic Self-Advocacy Network, and the National Disability Rights Network, but not including the Autism Society of America, which Weiss says, was contacted but refused to sign), the U.S. Department of Justice says it's opened a "routine investigation" of the infamous Judge Rotenberg Center in Canton, Massachusetts.

The investigation will seek to determine whether the JRC's practices violate Title III of the Americans with Disabilities Act, which prohibits discrimination against people because of their disabilities by any government agencies, nonprofit organizations, or private businesses that serve the public.

The initial letter of complaint that Nancy Weiss sent to the Justice Department (and also to the U.S. Department of Education, the U.S. Department of Health and Human Services, the Office on Disability within HHS, and to committees within both houses of the U.S. Congress whose areas of focus include education, and also to three international human-rights organizations: Amnesty International, Human Rights Watch and Physicians for Human Rights) spoke of the electrical shocks meted out to students every day at the Judge Rotenberg Center in broad terms as human rights violations; the language specific to the Americans with Disabilities Act and nondiscrimination appeared later, after the Justice Department responded that it may not have jurisdiction to enforce human-rights laws in a private facility, since the relevant law --- the Civil Rights of Institutionalized Persons Act --- applies only state-run institutions.

The logic in making this a claim of discrimination goes as follows:

(Quoted from Nancy Weiss's letter to the co-signers and other supporters of her September 2009 letter of complaint).

I suggested to [the Department of Justice] that they consider jurisdiction under the ADA on the basis that people with disabilities are being treated in ways that are neither legal nor would be tolerated if applied to people who do not have disabilities ... .

There's no way of knowing how long the investigation will take, but I am enormously glad the federal authorities are at least looking into it. What goes on at that "school" is nightmarish, and no living thing ought to be subjected to such treatment.

Friday, February 26, 2010

In or Out? Using Spatial Metaphors to Describe Autism

EXECUTIVE SUMMARY: People often use spatial metaphors to talk about autism. Ian Hacking, in his article "Autistic Autobiographies," points out that autistic autobiographies are often described (sometimes even in their own titles) as attempts to "go inside the mind" of their autistic authors. That expression compares "the autistic mind", which is usually considered interchangeable with the author's own mind, to an exotic foreign country rarely visited by outsiders. I would add a few other categories of spatial metaphor to Hacking's observation: first, autism (not "the autistic mind," but Autism itself, whatever the speaker imagines that to be) as foreign country; second, autism as fortress, prison cell or container --- the autistic person is "inside" while the world is kept "out" --- and third, autism as vast, uncrossable distance between people. I think all of these metaphors can be seen as outgrowths of a larger metaphor that linguists George Lakoff and Mark Johnson discuss in their book Metaphors We Live By: that metaphor compares communication to sending physical objects from one person to another through physical space.

I've noticed this trend for a while --- the trend of speaking and writing about autism like it's a place or a container that you can be inside or outside of --- and have long been planning to write about it, so I figure I might as well (start to) do that now.

The philosopher Ian Hacking mentioned this as well in the talk he gave at a 2008 conference on cognitive disability and moral philosophy, which has now been rewritten as an article in Philosophical Transactions of the Royal Society B, on autistic autobiographies, parents' stories of raising their autistic children, works of fiction featuring autistic characters, and the media and journalistic commentary about all of these, and about autism in general.
My own list of autistic fictions has approximately 200 books, and counting. Especially important are the stories for children, some for autistic children, some for non-autistic children, and some for all children. They take great pains to describe behaviour and thereby serve as role models. The young adult category is also influential in determining what autism is like and in some sense should be like. They illustrate 'the norm' and thereby help stabilize what the norm should be. Detective stories, spy thrillers, science fiction, gothic horror and Harlequin romances all help to reinforce a way of talking about autism.

(The article, as it appears in print, is titled "Autistic autobiography"; in lecture format, it was called "How We Have Been Learning to Talk About Autism." I think the latter title is more accurate, since Hacking deals with conceptions of autism in non-autobiographical writing as well, even though he does spend lots of time on autistic autobiography and award it special significance).
The story-tellers learn from autobiographies how to tell their tales. But that is a two-way street. Temple Grandin's Emergence was written before the genre got underway, so her self-descriptions are unaffected. Today's autistic child, brought up on children's stories about autistic children, and who in later years goes on to write an autobiography, will give accounts that are textured by the early exposure to role models.
Hacking goes on to list examples of one particular metaphor that recurs throughout autism autobiographies, and especially in the text used to describe them: the back-cover snippets, the capsule summaries, reviewers' summation, etc. --- the expression of going 'inside' autism. Sometimes autism might be a container or vessel, with mysterious contents that are only now being revealed and made accessible to us, the readers; sometimes it's a place we can visit.
In his foreword to Grandin (2005) [link], Oliver Sacks wrote that her previous book, Emergence, was
Unprecedented because there had never before been an 'inside narrative' of autism; unthinkable because it had been medical dogma for forty years or more that there was no 'inside,' no inner life, in the autistic. (Sacks, foreword in Grandin 2005, p. 11)

Even before we dip into these books, we find that word 'inside' over and over again --- on their covers. On the back cover of a current paperback of Grandin's (2005) Emergence:

A remarkable story ... uniquely valuable in helping us to see autism from the 'inside'.
A quotation from People magazine on a paperback of [Donna] Williams' Nobody Nowhere [link]:
By turns fascinating and harrowing ... a riveting autobiography that describes how autism feels like from the inside.
The subtitle of Mukhopadhyay's (2008) [link] is:
Inside my Autistic Mind.
The subtitle of the American edition of Tammet (2006) [link] is:
Inside the Extraordinary Mind of an Autistic Savant.
'Inside autism', in such phrasings, tends to be used more or less interchangeably with 'inside [Individual Autistic Person]'s mind', which Hacking finds terribly problematic:
When 'inside' connotes written or spoken by a person with autism, and 'outside' connotes written or spoken by an observer, parent, clinician or friend, then the metaphor is benign. But it is also, once the point has been made, rather banal, and hardly worth the constant repetition we have encountered.

Aside from such benign uses, I am cautious about 'inside the mind', for reasons presented in Wittgenstein's Philosophical Investigations. This is not the occasion to argue the case or even sketch what is at issue, but it does motivate my approach. It is certainly not a hankering after behaviourism.

A first danger of the 'inside' metaphor needs only be stated to be scotched. It is the idea of 'a unique insight into the autistic mind': as if 'the autistic mind' were a species of mind. Our four autists [Temple Grandin, Donna Williams, Daniel Tammet and Tito Mukhopadhyay] have very different minds! Grandin described herself as thinking in pictures. Mukhopadhyay is dominated by sounds. Tammet sees abstract objects in colour. Hence Williams' (2005) metaphor of autistic spectrum 'fruit salads'. To quote a common adage: 'If you know one autistic person, you know one autistic person.'

Talk of getting inside the mind of another is apt in its place, but unreflective use out of context often suggests a misleading picture of mental life. It suggests that looking inside is much like looking outside, in the way that looking inside a cardboard box after opening it is no different from looking at it from the outside, except for a change in point of view. This goes along with the sense that our own minds are transparent to us (subject to Freudian reservations). We look inside them all the time. That generates the question of how we ever know what is going on in the mind of another person.
There can always arise particular difficulties in understanding another person. But the puff writers who talk of getting into the mind of an autistic person do not, for a moment, think that there is the same general question for most people, as there is for autists. I cannot recall an 'inside the mind' (or any variant thereof) being written on the cover of any non-autistic autobiography that I have examined lately. It could certainly occur, of course, with a biography. 'Finally we have got inside the inscrutable mind of Vladimir Putin.' But that is not the norm.
I have more to add to Hacking's cursory listing of examples of the 'inside autism' metaphor:

The subtitle of the anthology Women from Another Planet? is "Our Lives in the Universe of Autism".

The synopsis on the back of my copy of Judy and Sean Barron's There's a Boy In Here (Simon & Schuster, 1992; hardcover) says, "Autism From the Outside In... / ... And From the Inside Out"; on the front cover there's the text "A mother and her son tell the story of his emergence from autism." The jacket text of There's a Boy In Here is especially full of in/out metaphors:
[T]hough nothing seemed to work, [Sean's parents] sometimes caught fleeting glimpses of the helpless child inside the stranger who shared their home. They were determined to free him, and somehow their love, their rage, their patience, their sheer humanness reached him at last ... [H]e remembers ... the terrifying isolation, the desperate desire to reach out ... until his family's indomitable and courageous resolve finally released him. ... [T]he poignant self-portrait of a boy trapped in a maze of compulsion and obsession.
In Nobody Nowhere, Donna Williams talk about living in "[her] own world" as a child; she draws a distinction between her world and The World, which is outside her, around her and mutually exclusive with her world. In a poem that acts as an epigraph to the book, she writes of "a world under glass" where sensations are dulled, and you think nothing can reach you, but where you're utterly alone:
In a world under glass, you can watch the world pass,
And nobody can touch you, you think you are safe.
But the wind can blow cold, in the depths of your soul,
Where you think nothing can hurt you till it is too late.

The titles of a lot of books, too, reflect a spatial metaphor: There's a Boy In Here; Emergence; The Siege --- all of these rely on a metaphorical understanding of autism as something that people become trapped in and have to be rescued, or rescue themselves, by a heroic effort (their own, someone else's or both); autism is not only a place, it's a place that's very hard either to get into from outside or to get out once you're inside. Autism as Death Star.
A later edition of There's a Boy In Here has the subtitle "Emerging from the Bonds of Autism."

Finally, all the images I have included in this post appeared when I did a Google Image search for "autism" --- all were illustrations for (sometimes mis-)informational websites on autism. I chose ones that I felt reflected the metaphor in a visual way: metaphors are not just for verbal thinkers!

Particularly, I feel there are subspecies within this category of metaphor that are worth identifying more precisely. Right now, I can think of three:

(1) Autism as prison cell/container
(2) Autism as (very large) distance between people
(3) Autism as unknown territory

I would also date the usage of the parent metaphor to all three of these --- autism as a discrete part of physical space --- earlier than the earliest autiebiographies; there was writing about autism for some decades before Temple Grandin wrote her first book, Emergence. While this earlier writing may or may not have influenced her way of thinking about her autism, it had certainly been informing the larger culture into which her story has become assimilated.

Even the title she chose for this work partakes of the metaphor whose ancestry I'm trying to trace here --- what is she emerging from? Is it autism in general, or one particular aspect of it she had to transcend to come into herself?

(This latter possibility occurs in Dawn Prince-Hughes' much-later autiebiography, Songs of the Gorilla Nation, in which she describes herself moving within the metaphorical terrain of autism, from its dark regions into its "beauty." So that's another possibility for the autism-as-geography subtype of autism-as-place/container: movement occurring within "autism". It also raises the possibility that "autism" is not a flat, uniform piece of terrain, and that different autistic people might inhabit different parts of that vast country).

Anyway, before Grandin wrote her hugely influential works, there was already a body of literature on autism: books written for popular consumption by clinicians, and personal narratives by parents of autistic children, of which the oldest is (as far as I know) Clara Claiborne Park's 1967 book The Siege: A Family's Journey into the World of an Autistic Child. Both the title and subtitle suggest that Jessy Park's autism is a physical place to be ventured into; calling that process a "siege" implies that this hidden realm has walls that its besiegers have to breach, and defenses they have to overpower; that autism is not always an inert landscape -- however forbidding --- but sometimes actively resists exploration.

One thing the autism-as-container metaphor tends to leave muddled is where the autistic person dwells in this metaphorical space. It's quite eloquent on the position of the parents, peers and teachers struggling to relate to this strange being --- we're given to understand quite clearly that they feel locked out and exhausted from battering at the door --- but what's not always clear is whether the autistic person is in the metaphorical Fortress of Solitude, or whether they are it.

Judy and Sean Barron's 1992 book There's a Boy in Here makes it unusually clear: Sean is inside his autism, his thoughts, feelings, desires and self obscured from his mother's sight by his intense anger, his tantrums, his reckless, aggressive and often-destructive behaviors. But in other books, like The Siege (which I haven't read) or Bruno Bettelheim's mother-blaming opus The Empty Fortress (which I likewise haven't read), it's not clear whether the walls that the authors advocate tearing down imprison the child, or whether they constitute a part of hir, like a protective cocoon or exoskeleton. The act of trying to "break through" to an autistic child becomes a violent one if the latter construction is implied, but, for Bettelheim at least, it would be logically impossible --- a bad metaphor, to say the least --- for anything to be in the "empty fortress", so it looks to me like the only way to interpret that one is that the autistic child's mind is the fortress, and Bettelheim was trying to tear it down and rebuild it to his liking.

Sometimes autism might be spoken of metaphorically as distance; I listed this as a third subtype of the autism-as-place metaphor, since in this case autism is not where the autistic person is so much as it the space between the autistic person and everyone around hir who isn't autistic, but now that I think about it more I've decided it functions more or less identically to the autism-as-container subtype. In both, autism is the barrier between the autistic person and the people seeking to understand or relate to hir; in both, the barrier must be overcome.

The autism-as-distance and autism-as-container subtypes of the autism-as-place metaphor also seem to me to be related to the larger, implicit metaphor described by George Lakoff and Mark Johnson in Metaphors We Live By: the "complex metaphor" of communication as sending bits of meaning packaged in language along a conduit to another person. If communication is thought of as analogous to sending things through space, it makes sense that anything that makes communication harder (like a difference in neurotypes between sender and receiver) will be translated into this metaphor as a physical barrier.

Thursday, February 11, 2010

More Proposed DSM Revisions

Besides the unification of all the autism-spectrum conditions under a single, simplified definition (which I generally consider a Good Thing, despite the reservations I mentioned in my earlier post; this post of Amanda Forest Vivian's captures what I think is good about it quite well) and the elimination of Rett's Disorder from the DSM entirely, the DSM-V revisions include lots of other interesting ideas.

These include:

- Adding Binge Eating Disorder to the Eating Disorders category

- Eliminating amenorrhea (loss of one's mentrual period) from the criteria for Anorexia Nervosa, which would finally allow men who meet all of the remaining criteria to be diagnosed with full-blown anorexia rather than with the vague, often-minimizing label Eating Disorder Not Otherwise Specified

- Adding a childhood mood disorder called Temper Dysregulation with Dysphoria, which would be characterized by irritability and frequent temper tantrums; this disorder is meant as an alternative diagnosis for many of the children who are (or would be) now diagnosed with bipolar disorder

- Consolidating the personality disorders into five broad, yet-to-be-determined categories

- Adding "Hypersexual Disorder" and Paraphilic Coercive Disorder (in which the person is turned on by the idea of raping another person) to the Sexual and Gender Identity Disorders category

- Expansion of the DSM-IV's Substance-Related Disorders category (which included substance dependence and abuse) to a broader Addiction and Related Disorders category, which will include non-chemical, "behavioral" addictions like gambling; Internet addiction was considered for inclusion in this category, too, but ultimately discarded

Some of these proposed changes --- the two eating-disorder changes I mentioned, as well as the decision to remove some problematic wording from the criteria for anorexia, for instance --- are unadulterated Good Things, and were very much needed. (I'd actually argue, along with Rachel and her commenters, that the reforms to the anorexia criteria didn't go far enough; that BMI should not be the gauge of severity of anorexia because it misses those people who might be restricting their eating and obsessing about food, weight and body image just as severely as someone with diagnosable Severe Anorexia, but who, due to individual metabolic variation, never become underweight.) Others, like the addition of Temper Dysregulation with Dysphoria as a new childhood disorder, the concept of "risk syndromes" for psychosis and dementia, are a mixed bag. They might be helpful, or they might result in more people being marginalized, losing autonomy and/or being pressured to take powerful antipsychotic medications for illnesses that, in the case of the risk syndromes, aren't even present and may never be.

Also in the mixed-bag category is the DSM-V's formulation of Gender Identity Disorder (renamed Gender Incongruence, in an attempt to be less stigmatizing), which it splits into two main categories, one for children and one for adolescents and adults. Good things about the new criteria include the aforementioned move toward value-neutral language, its acknowledgement that sex and gender, even for transgendered people, aren't always binary (there's a long history of doctors "gatekeeping" sexual reassignment surgery, hormone therapy and other medical procedures associated with transition, restricting these things to those trans people who conformed most rigidly to the conventional role of their chosen gender) and its stress on whatever the individual trans person wants as the desired outcome. What's not as good is the retention of the notion of autogynephilia --- sexual fetish as motivation for transition --- in the category of Transvestic Fetishism, and the presence of stricter, gender-binary-enforcing language in the criteria for pediatric Gender Incongruence.

Finally, the creation of Hypersexuality as a new sexual disorder strikes me as colossally wrongheaded. Like sexual addiction --- which is not recognized in the DSM-IV, but which has gained popular acceptance in the addiction-recovery community --- this category would be inherently biased against people with unconventional sexualities: kinky people, swingers, polyamorists, even, depending on how conservative a community the person being evaluated comes from, gay and bisexual people. I also disapprove of the existence of this category for the same reason I disapprove of Hypoactive Sexual Desire Disorder: merely wanting/having sex to a greater or lesser degree than most people do isn't pathology, it's variation.

Wednesday, February 10, 2010

DSM-V Draft Posted Online

The American Psychiatric Association has posted its proposed revisions to the Diagnostic and Statistical Manual of Mental Disorders on its website, where specific disorders are grouped by category.

Here are the (current, subject to further revision) proposed criteria for Autism Spectrum Disorder in the DSM-V:
Autism Spectrum Disorder

Must meet criteria 1, 2 and 3:

1. Clinically significant, persistent deficits in social communication and interactions, as manifest by all of the following:

a. Marked deficits in nonverbal and verbal communication used for social interaction;
b. Lack of social reciprocity;
c. Failure to develop and maintain peer relationships appropriate to developmental level.

2. Restricted, repetitive patterns of behavior, interests, and activities, as manifested by at least TWO of the following:

a. Stereotyped motor or verbal behaviors, or unusual sensory behaviors
b. Excessive adherence to routined and ritualized patterns of behavior
c. Restricted, fixated interests

3. Symptoms must be present in early childhood (but may not become fully manifest until social demands exceed limited capacities).
This category includes everyone who, under current DSM-IV guidelines, would be diagnosed with Autistic Disorder, Asperger's Disorder, Pervasive Developmental Disorder Not Otherwise Specified, and Childhood Disintegrative Disorder. Rett's Disorder is also included in the DSM-IV section on pervasive developmental disorders, but is slated for removal from the DSM-V:
Rett's Disorder patients often have autistic symptoms for only a brief period during early childhood, so inclusion in the autism spectrum is not appropriate for most individuals.

Like other disorders in the DSM, Autism Spectrum Disorder (ASD) is defined by specific sets of behaviors and not by etiology (at present) so inclusion of a specific etiologic entity, such as Rett's Disorder, is inappropriate. To ensure that etiology is indicated, where known, clinicians will be encouraged to utilize the specifier: "Associated with Known Medical Disorder or Genetic Condition." In this way, it will be possible to indicate that a child with ASD has Fragile X syndrome, Tuberous Sclerosis, 22q deletion, etc.
This strikes me as reasonable; autistic-like behaviors that are part of a wider, underlying syndrome should be recognized as part of that syndrome, rather than considered or treated in isolation. Michelle Dawson, noting that "the vast majority of named neurodevelopmental disabilities do not appear in the DSM, past, present, or future", suggests that autism doesn't belong there, either.

Back to the revised criteria for Autism Spectrum Disorder: I noticed that there are now two, rather than three, symptom domains --- communication and social interaction have been merged into one category, leaving a "social communication and interactions" domain and a "restricted interests/repetitive behaviors" domain. The criteria seem to be vaguer, more flexible versions of the earlier autism criteria, which, as Shiva has written about recently, dwell excessively on social and communication impairments while ignoring other areas of difference that are just as important, if not more so, in the lives of individual autistics:
IMO, the existing "triad of impairments" [which the UK's National Autistic Society defines, somewhat differently from the APA's DSM-IV, as "difficulty with social communication," "difficulty with social interaction," and "difficulty with social imagination"], even with the additional "related characteristics" [of, among other things, "sensory sensitivity," "special interests," and "love of routines"] ... fails at defining autism both by inaccuracy in what it does contain and by failing to include what many autistic people consistently report as among the most significant components of what distinguishes us from neurotypical people.
Michelle Dawson criticizes this reductiveness, too, although her criticism deals more with the DSM-V workgroup failing to incorporate any understanding of autism as a separate cognitive phenotype, rather than one fundamentally equivalent to the standard, neurotypical cognitive phenotype, but missing some very important social and communicative bits.

I don't think, nor does much of the research on autistic cognition and perception suggest, that anything like that is the case.

Wednesday, February 3, 2010

A Popular Mis-Conception

This post of Urocyon's, about zoologists who can't seem to stop describing animal behavior in terms that reflect the values and norms of one particular human culture*, reminded me of the chapter in Natalie Angier's Woman: An Intimate Geography about the ovum and how its role in reproduction is commonly (and wrongly) understood in terms of traditional Western conceptions of gender: Man acts, Woman is acted upon; Man creates, Woman nurtures, etc.
One of the more obvious, and literal, examples of applying this gendered binary to human reproductive biology is the understanding of conception shown in Book I of Aristotle's On the Generation of Animals:
That, then, the female does not contribute semen to generation, but does contribute something, and that this is the matter of the catamenia [menstrual blood?], or that which is analogous to it in bloodless animals, is clear from what has been said [earlier in the passage], and also from a general and abstract survey of the question. For there must needs be that which generates and that from which it generates; even if these be one, still they must be distinct in form and their essence must be different; and in those animals that have these powers separate in two sexes the body and nature of the active and the passive sex must also differ. If, then, the male stands for the effective and active, and the female, considered as female, for the passive, it follows that what the female would contribute to the semen of the male would not be semen but material for the semen to work upon. This is just what we find to be the case, for the catamenia have in their nature an affinity to the primitive matter.
[W]henever one thing is made from two of which one is active and the other passive, the active agent does not exist in that which is made; and, still more generally, the same applies when one thing moves and another is moved; the moving thing does not exist in that which is moved. But the female, as female, is passive, and the male, as male, is active, and the principle of the movement comes from him. Therefore, if we take the highest genera under which they each fall, the one being active and motive and the other passive and moved, that one thing which is produced comes from them only in the sense in which a bed comes into being from the carpenter and the wood, or in which a ball comes into being from the wax and the form.
This understanding dominated biology from the days of ancient Greece until the 18th century; some early biologists, like Nicolaas Hartsoeker, took this idea of sperm-as-seed/womb-as-flowerpot to its logical extreme of thinking there was a tiny person already fully-formed inside the sperm cell! (Hartsoeker is the one who drew the cute little sketch shown near the top of this post. There's even a little star inside its tiny head, which I'm guessing represents a soul).

Even once the actual mechanics of fertilization became known, and people realized that women's ova also contain genetic material**, there was still a tendency to describe the male and female gametes' roles in Aristotelian terms of passive, receptive egg and moving, active sperm. The sperm are said to compete against each other to reach the egg, thereby ensuring that the hardiest, best one goes on to develop into an embryo.

The truth is actually more complicated, and involves more of an interplay between egg and sperm.

I don't currently have Angier's book on hand --- my partner, a sometime anatomy teacher and amateur sex educator, is borrowing it --- but I do have my developmental-biology textbook from college, Scott F. Gilbert's Developmental Biology, Seventh Edition. It ought to include everything Angier mentioned, and probably more, too.

Anyway, four processes that occur in the egg stick out to me as giving the lie to the notion of the female gamete as an inert substrate, awaiting the action of the "winning" male gamete:

1) In order to find the egg at all, sperm depend on signaling molecules secreted by the egg, which allow the sperm to track where the signals are coming from and adjust their trajectories accordingly.

2) Sperm undergo a chemical transformation called capacitation once they've been in the uterus for a while, without which they're unable to pass through the cumulus, or layer of ovarian follicular cells associated with the egg. During capacitation, the sperm cell membrane changes composition: uterine proteins remove cholesterol, and some of the proteins and carbohydrates embedded in the sperm cell membrane are also stripped away. The membrane also hyperpolarizes (i.e., the difference in net electrical charge between opposite sides of the membrane becomes bigger), which somehow triggers a cascade of protein phosphorylations (which, as I've mentioned before, can either activate or inhibit a protein) which ultimately allows the sperm to recognize, bind to and fuse with the egg.

3) For the sperm to be able to release its genetic material into the egg, a protein in the egg's zona pellucida, or thick outer coating of glycoproteins, has to bind to the sperm and initiate a process called the acrosome reaction, which is a signaling cascade involving G proteins (I've written about them before, too) and a mass influx of calcium ions, set off by surface proteins on both sperm and zona pellucida weaving together, and which results in the release of the protein-digesting enzymes contained in the acrosomal vesicle. These enzymes bore a tunnel through the zona pellucida that allows the sperm to reach the egg cell membrane.

4) Once a given sperm cell has fused membranes with the egg, another chemical reaction takes place, modifying zona-pellucida proteins so that they can no longer bind to any additional sperm-cell surface proteins. This causes the swarm of sperm cells that has gathered around the zona pellucida to lose their grip on it and disperse before any more of them can deposit genetic material inside the egg.

So, the egg guides the sperm toward it, draws it in as it approaches, triggers the acrosomal reaction that allows the sperm to penetrate the dense zona pellucida, and, once that sperm has fused with the egg and deposited its genetic material inside it, it prevents any others from doing likewise.

"Material for the semen to work upon," indeed!

*Have a guess as to which one. No prize if you said "white Christian Anglo-American capitalist patriarchy," sorry!

**The egg actually contributes a bit more DNA to the eventual embryo than the sperm does, for two reasons: 1) sperm cells can have either an X or a (much smaller) Y chromosome, while the egg always has an X; and 2) sperm cells are super-streamlined, containing only a nucleus and a sac of cell-membrane-dissolving chemicals called an acrosomal vesicle within their cell bodies, while the egg has a normally-sized and -populated cytoplasm, which includes mitochondria, which have their own vestigial genomes. (Sperm have mitochondria, too, but they're associated with the flagellum and do not enter the egg during fertilization).

Tuesday, February 2, 2010